• Rain cap is necessary: Avoid the mount threads exposed to accumulate dirt and to corrode
• Radio antenna base nut: Effectively protects the unused NMO antenna in all environments
• O ring Seal in the Base: keep water out. And there is an inner ring to protect the contact pin
• Waterproof: The rain cap the best way to keep your NMO mount dry when washing your car
• Compact Design: Very handy to use, perfect snug and sturdy