Replacement buffer spring is the medicine to cure cycling problems caused by spring fatigue. Made of high-grade coil spring steel that retains its full elasticity over thousands of compression cycles, to help ensure your rifle keeps running smoothly. Properly finished ends won't damage the inside of the buffer tube or the face of the buffer. If your formerly reliable rifle starts having cycling problems with the loads it used to like, even after a thorough cleaning, replacing the inexpensive recoil spring may be the only fix required to get it back "up to snuff". For use only in M4-type receiver extensions with a carbine-weight recoil buffer.