Now released by Tokyo Marui is their High Mount Ring. It has a mount base of 20mm making it compatible to most, if not all, Picatinny-standard rails. The inside diametre of the rigng is 25.4mm or 1 inch, corresponding to optics with 25.4mm diamters. It can installed at a height of 30.7mm from the top of the mount of the mount base to the tube centre of the optics and 18mm to the bottom of the tube.