Seals for headlights, tail lights, indicators ...

Moisture is one reason why the electrical system on a Harley can fail. Water is an excellent electricity conductor and if, after riding through the rain or steaming off in the wash box, water is left in the blinkers, for example, you’ll end up quickly with a short circuit in the bulb socket. The right seal or O-ring will cure the issue and avoid moisture.

Due to the large number of different manufacturers and suppliers, some headlight inserts do not fit perfectly into the chrome rings of the housings. An O-ring has often proved its worth as a "gap mediator". So: no swear nor sweat, look for an O-ring instead.