The Weaver / Picatinny mounting system uses a single locking bolt that is housed in the rifles rail and clamps the mount onto the rail. The locking bolt is a nut shape and it can be tightened with a spanner or an allen key can be put through a specially drilled hole and then levered tight.
The double allen key tube locking system and the cushion/grip tape, lock the scope in position and prevent it from damage and movement.

Size: Medium - 30mm