Appliances
Washers, refrigeration, HVAC, and cooking equipment where glow-wire capable housings and 600V margins matter.
Molex 3.5mm power Fit connectors
Molex Ultra-Fit connectors for compact 600V power
Select Ultra-Fit single-row or dual-row tangless housings, 172253 terminals, TPA and CPA options, keying color, wire range, and circuit count for compact power harnesses.
3.50mm Pitch2-16 Circuits16-22 AWG600V
Why Molex Ultra-Fit connectors exist
Molex Ultra-Fit is the 3.5mm Fit family for compact power. It sits between Micro-Fit 3.0 and Mini-Fit Jr., carrying 16 AWG wire and up to 14A per circuit in a footprint closer to Micro-Fit.
Current tangless housings include 172256 single-row receptacles for 2-8 circuits and 172258 dual-row receptacles for 4-16 circuits, both glow-wire capable nylon. A robust-latch single-row variant ships as series 228824.
Terminal options are 172253 tangless female crimp terminals in tin or gold, split by wire range into 18-16 AWG and 22-20 AWG versions. Accessories include 172264 TPA retainers and 217185 CPA locks.
MiniProto stocks single-row and dual-row Ultra-Fit receptacle housings from 2-16 circuits in the live configurator catalog.
Why teams choose Molex Ultra-Fit
Ultra-Fit is the Fit choice when the design needs Mini-Fit-class current in a smaller connector, with a 600V rating and appliance glow-wire options.
Current Density
Up to 14A on 16 AWG in a 3.5mm pitch body, so short power runs stay compact without stepping up to a 4.2mm family.
600V Rating
The connector-level rating is 600V AC or DC, sized for line-voltage appliance and equipment power inside an enclosure.
Assurance Options
Tangless terminals, TPA retainers, CPA locks, and color polarization keep terminals seated and mis-mating out of the build.
Where Molex Ultra-Fit earns its place
Industrial Power
Machine internals, control cabinets, and power supplies routing branch power to boards and modules.
Lighting And Equipment
High-bay lighting, battery-powered equipment, and power rails where space is tighter than a Mini-Fit Jr. layout.
Fit family comparison
Pick the Fit family by pitch, wire range, circuit count, and the exact terminal and wire condition behind the current rating.
Nano-Fit
Compact signal and power, tight packaging
2.5mm
20-26 AWG
- Max Current*
- 8.0A with 105300 terminals and 20 AWG in a 2-circuit wire-to-board set
- Circuits
- 2-8 single / 4-16 dual
Micro-Fit 3.0
Mid-density power and signal workhorse
3.0mm
18-30 AWG
- Max Current*
- 8.5A with 43030 terminal and 18 AWG
- Circuits
- 2-12 single / 2-24 dual
Ultra-Fit
Compact 600V power with glow-wire options
3.5mm
16-22 AWG
- Max Current*
- 14A with 172253 tin terminals and 16 AWG in a 2-circuit single-row wire-to-board set
- Circuits
- 2-8 single / 4-16 dual
Mini-Fit Jr.
Classic power interconnect
4.2mm
16-28 AWG
- Max Current*
- 9A with 5556 terminal and 24-18 AWG variant; 13A with 45750 HCS terminal and 16 AWG
- Circuits
- 2-24 dual
Mega-Fit
High-current power runs
5.7mm
10-16 AWG
- Max Current*
- 23A at 600V with Mega-Fit terminals and 12 AWG; 30A peak with Mega-Fit terminals and 10 AWG in a 2-circuit wire-to-wire set
- Circuits
- 2-8 single / 2-12 dual
| Family | Pitch | Max Current* | Wire | Circuits | Use |
|---|---|---|---|---|---|
| Nano-Fit | 2.5mm | 8.0A with 105300 terminals and 20 AWG in a 2-circuit wire-to-board set | 20-26 AWG | 2-8 single / 4-16 dual | Compact signal and power, tight packaging |
| Micro-Fit 3.0 | 3.0mm | 8.5A with 43030 terminal and 18 AWG | 18-30 AWG | 2-12 single / 2-24 dual | Mid-density power and signal workhorse |
| Ultra-Fit | 3.5mm | 14A with 172253 tin terminals and 16 AWG in a 2-circuit single-row wire-to-board set | 16-22 AWG | 2-8 single / 4-16 dual | Compact 600V power with glow-wire options |
| Mini-Fit Jr. | 4.2mm | 9A with 5556 terminal and 24-18 AWG variant; 13A with 45750 HCS terminal and 16 AWG | 16-28 AWG | 2-24 dual | Classic power interconnect |
| Mega-Fit | 5.7mm | 23A at 600V with Mega-Fit terminals and 12 AWG; 30A peak with Mega-Fit terminals and 10 AWG in a 2-circuit wire-to-wire set | 10-16 AWG | 2-8 single / 2-12 dual | High-current power runs |
*Max current is the best case from Molex family data. Real limits come from the exact terminal, wire, circuit count, ambient temperature, and housing selected.
Choose Ultra-Fit when the selected terminal and 16 AWG wire condition needs more current than Micro-Fit 3.0 but the package cannot grow to Mini-Fit Jr. pitch. For heavier wire than 16 AWG, move up to Mega-Fit.
The Ultra-Fit limits that matter
Use Ultra-Fit for compact 3.5mm pitch power layouts. The 14A best case requires 172253 tin terminals, 16 AWG wire, and a fully loaded 2-circuit single-row set per Molex PS-172323-0001.
Electrical
- Pitch
- 3.50mm
- Peak Current
- 14A with 172253 tin terminals and 16 AWG in a 2-circuit single-row set
- Dual-Row 16-Ckt
- 10A with 172253 tin terminals and 16 AWG, fully loaded
- Voltage
- 600V AC (RMS) or DC max
Mechanical
- Single Row
- 2-8 circuits, 172256 or 228824 receptacles
- Dual Row
- 4-16 circuits, 172258 receptacles
- Cycles
- 25 tin, 200 gold
- Accessories
- 172264 TPA, 217185 CPA
Environmental
- Temperature Tin
- -40 to 125 C including T-rise
- Temperature Gold
- -40 to 120 C including T-rise
- Glow-Wire
- 172256, 172258, and listed header series, per IEC 60695-2-11 methods
- Wire Insulation
- 2.00mm max OD on 16 AWG, down to 1.30mm max on 22 AWG
Materials
- Housings
- Nylon, UL 94V-0
- Terminals
- 172253 tangless female, tin or gold
- Wire Ranges
- 18-16 AWG and 22-20 AWG terminal versions
- Approvals
- UL E29179, CSA LR19980
Reference data comes from Molex product specification PS-172323-0001 and manufacturer CAD models; verify final ratings against the exact selected contact and housing.
Positions, rows, and keying
Ultra-Fit circuit counts
Common 172256 single-row and 172258 dual-row tangless receptacle housing sizes. Single row covers 2-8 circuits, dual row covers 4-16.
2-Circuit
172256
4-Circuit
172258
6-Circuit
1722568-Circuit
172258
12-Circuit
172258
16-Circuit
172258
Use the exact selected Ultra-Fit sales drawing for cavity numbering. Circuit one sits at the keyed end, and single-row versus dual-row layouts number differently.
Color polarization and latch options
Ultra-Fit keys by housing color: black parts use one key option and natural parts the other, so a black receptacle will not mate with a natural header of the same circuit count. Pick one color scheme per interface and keep it consistent between harness and board.
Terminal position assurance is a separate 172264 TPA piece per circuit count, and 217185 CPA locks the mated pair. The 228824 robust-latch single-row housing swaps the standard latch for a heavier one where vibration or service handling demands it.
Black, key option 1Natural, key option 2
Ultra-Fit connector stack
What completes an Ultra-Fit connection
An Ultra-Fit connection combines a 172256 or 172258 receptacle housing, 172253 tangless terminals in the right plating and wire range, a mating header or plug, and optional TPA and CPA assurance parts.
Molex replaced the original tanged Ultra-Fit housings and terminals with tangless versions. Keep tangless terminals with tangless housings; the legacy tanged parts are obsolete and not interchangeable.
- Single-Row Housings
- 172256 standard, 228824 robust latchCovers 2-8 circuits, glow-wire capable nylon.
- Dual-Row Housings
- 172258Covers 4-16 circuits in the stocked family.
- Terminals
- 172253 tangless female, tin or goldSeparate part numbers for 18-16 AWG and 22-20 AWG wire.
- Assurance
- 172264 TPA, 217185 CPATPA is per circuit count; confirm against the selected housing.
Contact and accessory choices
Ultra-Fit terminal and wire selection controls the current condition. Use 172253 tin terminals for cost and 172253 gold versions where cycles or contact resistance demand them.
Tin And Gold Terminals
- Tin Female
- 172253 tin, 18-16 AWG or 22-20 AWG versions
- Gold Female
- 172253 gold, 18-16 AWG or 22-20 AWG versions
- Cycles
- 25 tin, 200 gold
- Resistance
- 2 milliohm tin, 3 milliohm gold, initial max
Current Conditions
- Best Case
- 14A with 172253 tin terminals and 16 AWG in a 2-circuit single-row set
- Dual 16-Ckt
- 10A with 172253 tin terminals and 16 AWG, fully loaded
- 22 AWG Floor
- 5A with 172253 tin terminals and 22 AWG in a 16-circuit dual-row set
- Gold Values
- Run below tin at the same condition, for example 12A at 2-circuit 16 AWG
For quoting, tie each current requirement to circuit count, row format, terminal plating, and wire gauge. Ultra-Fit is not one current rating across every part, and every table value assumes all circuits powered.
Wire size and current condition
Ultra-Fit terminals span 22-16 AWG across two terminal wire ranges. The 14A best case needs 16 AWG; dropping to 22 AWG roughly halves the table values.
Molex rates the tables at a 30 C temperature rise with all circuits powered, tested per EIA-364-70. Derate for ambient temperature, bundle heating, and the wire insulation rating, which can bind before the connector does.
Wire and fit checks
- Terminal Ranges
- 18-16 AWG and 22-20 AWG
- Best Case
- 14A with 172253 tin terminals and 16 AWG in a 2-circuit single-row set
- Dual 16-Ckt
- 10A with 172253 tin terminals and 16 AWG
- Insulation OD
- 2.00mm max on 16 AWG, 1.30mm max on 22 AWG
Final wire choice comes from the exact housing, terminal, insulation OD, bend radius, and bundle temperature. Gauge alone is not enough.
What drives cost
Ultra-Fit cost moves with terminal plating, wire gauge, circuit count, keying color, and the TPA and CPA assurance stack.
- Terminal Plating
- Tin lower, gold higherUse gold where 200 cycles or tighter contact resistance is required.
- Wire Gauge
- 22 AWG lower, 16 AWG higherHeavier wire raises material and crimp time but carries the headline current.
- Assurance Parts
- TPA and CPA add parts and assembly stepsSpecify them where vibration or service handling justifies the cost.
Stock and sourcing
MiniProto stocks single-row and dual-row Ultra-Fit receptacle housings across 12 connector entries from 2-16 circuits in the live configurator catalog. We quote terminal plating, wire gauge, keying color, and assurance parts together so the current condition stays intact.
Assembly, and the mistakes to avoid
- !Do not use the 14A value unless the build uses 172253 tin terminals, 16 AWG wire, and a 2-circuit single-row set; higher circuit counts and smaller wire rate lower.
- !Do not mix legacy tanged terminals or housings with the current tangless system; the tanged parts are obsolete and not interchangeable.
- !Do not pair black and natural parts on the same interface; color polarization keys them differently on purpose.
- !Do not treat glow-wire capability as universal. Confirm the exact selected part number carries the glow-wire designation.
Common questions
What is Molex Ultra-Fit used for?+
Molex Ultra-Fit is a 3.5mm pitch wire-to-board power connector family for appliances, industrial machinery, lighting, and equipment power rails where the design needs more current than Micro-Fit 3.0 in less space than Mini-Fit Jr.
How much current can Ultra-Fit carry?+
The best-case value in Molex product spec PS-172323-0001 is 14A with 172253 tin terminals and 16 AWG wire in a fully loaded 2-circuit single-row set. Ratings fall with circuit count and wire gauge: a fully loaded dual-row 16-circuit housing with tin terminals and 16 AWG is 10A, and 22 AWG dual-row values drop to 5A.
What is the difference between 172256 and 172258?+
172256 is the single-row tangless receptacle housing family for 2-8 circuits. 172258 is the dual-row tangless receptacle family for 4-16 circuits. Both take the same 172253 tangless crimp terminals.
Which terminals does Ultra-Fit use?+
Current Ultra-Fit housings use 172253 tangless female crimp terminals in tin or gold plating, with separate part numbers for 18-16 AWG and 22-20 AWG wire ranges. Legacy tanged terminals belong to obsolete housing versions and should not be mixed with tangless housings.
Is Ultra-Fit glow-wire rated?+
Molex lists 172256, 172258, and related header series as glow-wire capable, tested to IEC 60695-2-11 methods per the product specification. Confirm the exact selected part number carries the glow-wire designation before claiming it in an end product.
How is Ultra-Fit keyed?+
Ultra-Fit uses color polarization: black housings use one key option and natural housings the other, so same-circuit-count black and natural connector pairs cannot cross-mate. Optional TPA retainers and CPA locks add terminal and connector position assurance.
Build your Molex Ultra-Fit harness
Pick positions, contacts, and wire. See the price as you go, then send it to our floor.