This Part connects to the picatinny rail system. In order to fasten the part to the rail you need;

-M3 x 30 bolt

-M3n

-(Optional) Some sort of tool to cut the bolt to size.

If you have decided to cut the bolt to size, you must cut the bolt to 27mm IN OVERALL LENGTH(Head of bolt to tip). If you cut it to short, the bolt will not reach the nut and thus, not work.