Bought a 7cm rail to mount a vertical foregrip for my Perses, which has non-picatinny rails. Fits great on my nerf rails and now I can mount any picatinny rail attachment!
Comes with a tiny allen screw to tighten the rail down. Allen wrench is not included so use a microscrewdriver to get it reasonably tight.
These work great and I'm planning on using them for more Nerf projects in the future! (fast shipping too!)