Sooner or later.... - Anderson Manufacturing OOPS Spare Kit

There are two types of AR15 builders/maintainers... Those who have lost a spring or detent pin, and those who will.
Sooner or later, it will happen... During assembly or reassembly of your favorite AR15, the energy stored in a spring you are installing will be unexpectedly released, causing the spring (and perhaps its associated detent pin) to launch like a Trident missile into regions of your workshop where no man has gone before. A corollary to Murphy's law states that the probability of locating its resting place is inversely proportional to the importance of the spring.
What to do? If you have this kit, the project continues. Otherwise, it's on hold till you track down a replacement. This kit provides spare springs and pins to allow the rifle assembly to be completed after turning the air only SLIGHTLY blue... Reasonable cost insurance against the inevitable.