Three Options available with these new mounts One Piece Picatinny Rail Mounts Features Extra Heavy Duty 12 screw, Heavy Duty Bronze with Level bubble, Heavy Duty Black with Level bubble These fasten to any picatinny rail or 2-piece weaver mount system(see specs) These rails are suitable for all aspects of application. They are tried and tested on Bolt and Semi Auto rifles and Shotguns. The rings are 30mm with form fit adapter for 25.4mm Ideal for heavy optics or Thermal The mount system can be removed (ON/OFF) so that optics can be changed (ie Thermal at Night – Glass daytime) Separate mounts required for each optic Level bubble with heavy duty only Top Mount Ring Rail(front and rear ring) – ie laser/torch/red dot mount Extra Heavy duty (12 screw) 50mm Centre (ie cross slots) Heavy Duty with level 70mm Centre. Two piece weaver will have to suit the specs (or die grind to modify)