Picking the right wire seal: it's the insulation diameter, not the wire size
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Sealed connectors keep water out with two parts: the housing's interface seal and a wire seal on every cavity. The wire seal is the one everyone gets wrong — because people pick it by wire cross-section (mm²), while the seal doesn't touch the conductor at all. It seals on the outside of the insulation.
Why mm² isn't enough
Two wires with the same 1.0 mm² conductor can have very different outer diameters: thin-wall FLRY-B runs about 1.9 mm OD, while thick-insulation types are well over 2.5 mm. Same terminal, different seal. Pick the seal by mm² and you get either a seal the wire won't enter, or one that lets water creep along the insulation.
How to choose, in three steps
- Pick the terminal by conductor size (mm² / AWG) — that's the electrical match.
- Measure the insulation OD with calipers, or read it from the wire datasheet. Our wire listings state the nominal insulation OD for exactly this reason.
- Pick the seal whose range covers that OD. Every seal in our catalogue lists its insulation-OD range, and the product pages cross-link compatible seals per housing.
Example: Superseal 1.5
The TE Superseal 1.5 family uses the 281934-series single-wire seals, colour-coded by insulation OD:
- Green — 1.2–1.6 mm OD (very thin-wall, small gauges)
- Yellow — 1.7–2.4 mm OD (covers most FLRY-B 0.5–1.5 mm² — the one you'll use most)
- Red — 2.5–3.3 mm OD (thicker insulation)
Note these are all for the same terminals — the colour says nothing about wire gauge, only insulation OD.
Watch out for family look-alikes
Wire seals from different connector families are not interchangeable, even when they look similar: a JPT/MCP 2.8 seal is made for a larger cavity than a Superseal 1.5 seal and will never seal properly in the wrong housing. Always match seal series to connector series first, then OD range. Our housing pages list the correct seals under compatible parts, so you can't grab the wrong family.
Empty cavities need plugs
An unused cavity is a hole in your sealed connector. Fit a cavity plug in every unpopulated position — they cost cents and keep the IP rating honest.
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