Rubber O-Rings wear out! Or they get lost. If your O-Ring is worn out, mangled or simply missing from the cap, it won't do much good in the way of keeping water out. These fit the NMO cap styled like the Tram 1290 and others. This is a quality O-Ring, having Durometer rating of 70A (hardness of the ring). It is a tough one to wear out. Made of Buna-nitrile (also called Buna-N) it meets
Aerospace Standard AS568A and is rated to 250 degree F (heat is what wears out a O-Ring in a automotive setting - just set your hand on the body on a hot sunny day and you will feel what wears out the O-Ring).

Quantity: 1 Package of 5 O-Rings (Does not include the cap, only the O-Rings. Cap shown is for illustrative purposes only)