The ADR cantilever mount is designed for mounting 30mm tubed telescopic sights onto a flattop style AR-15 rifle. The 2-inch offset of this cantilever mount positions the scope in a forward location, allowing the correct eye relief and head placement on an AR-15. This ADR mount will work best with scopes having four inches or less of eye relief (if more than four inches, use the ADR-X model).