I bought a lumenok # 2219 crossbow flat, I got an arrow with no insert , so where that flat knock should go instead is my lumenok, I had to carefuly sand it,be sure not to sand the cantacts. When It snugly fit inside my carbon arrow quite tight actualy, I pushed it up against the table until It lighted up and then gently and I do mean gently turned and pulled slightly outward until the light went off. Took it out and shot It , in the daytime lightly overcast, it lit up great watched it go to the target, glad I bought it, it will be my first arrow to "soon draw blood." Hope this helps, good luck .