Make sure to read the PS90 FAQ:
http://fnforum.net/viewtopic.php?t=4286
Also - the lowest optic is a mount for a Trijicon or Aimpoint. Its not so much a rail, but a specific mount that will work with those 2 optics. If you want an actual optic rail - Critical Dimension's new optic rail with built in backup sights is the lowest optic rail I have seen....
The larger cocking knob info with the link to buy is here:
http://fnforum.net/viewtopic.php?t=315
http://fnforum.net/viewtopic.php?t=4286
Also - the lowest optic is a mount for a Trijicon or Aimpoint. Its not so much a rail, but a specific mount that will work with those 2 optics. If you want an actual optic rail - Critical Dimension's new optic rail with built in backup sights is the lowest optic rail I have seen....
The larger cocking knob info with the link to buy is here:
http://fnforum.net/viewtopic.php?t=315