It really does have a spring... - FAB Defense GLSHOCK AR-15/M16/M4 Recoil Reducing Stock Polymer

For all those people saying there is no shock absorbing on this, you are 100% wrong. Put the buttstock back on, put the butt of the rifle on a table and push rifle down into buttstock, you will see about an inch of movement on the butt stock. The spring is located on the locking bolt on reciever. If you flip butt stock upside down and do the test you will see that locking bolt move back and forth in the release handle. This stock I hot as a gift, and I absolutely love it.