The BSA Multi-Purpose Sighting System is a wonderful light weight sight for close quarter and medium range targets. Light enough for small calibers plinking on the range, yet durable enough for larger calibers used by hunters and law enforcement departments. This sight features a 5/8 Weaver style attachment, an 11 position rheostat, and 5 MOA dot size.The RD30 is a 30mm red dot sight equipped with a 5/8 inches Weaver mount and 11 brightness settings. Features: Multicoated lens coating 50 yd parallax setting Unlimited eye relief Waterproof, shockproof, fogproof 11 brightness setting Limited 1 year warranty