The QD53-F adaptor is compatible with the PARD Predator FT34 & FD1-LRF front clip on night vision scopes. The adaptor comes with 3 separate nylon shims that accommodate scopes with an external eyepiece diameter between 42-53mm. This extra adaptor allows users to quickly and easily move the FT34 & FD1-LRF front clip on night vision scopes between different weapons.