Rain cap is necessary. Don't leave the mount threads exposed to accumulate dirt and to corrode. The rain cap the best way to keep your NMO mount dry when washing your car. Radio antenna base nut effectively protects the unused NMO antenna in all environments. Very handy to use. Perfect snug and sturdy. Package include: 2 pc antenna caps Rubber ring seal in the base to keep water out. And there is an inner ring to protect the contact pin. NMO Antenna Cap Injection molded plastic rain cap perfect for a NMO style antenna base.
Easy To Install Plug and play. The antenna cap can be easily screwed onto your antenna base within seconds.

PackList: NMO Antenna Cap x 2