The B5 Systems 556 Collapsible Precision Stock Provides An Adjustable Stock Solution For a Carbine Receiver Extension All too often in the past your only option for installing a precision rifle stock was to change the receiver extension on your rifle from a carbine to a rifle length. This could cause issues with finding the correct spring and buffer weight and in some cases would cause issues with perfectly functionally guns. Now all those headaches are behind you with the introduction of the B5 Systems Precision Stock designed to be a direct replacement for a mil-spec diameter carbine receiver extension. This forward thinking design allows you to maintain the carbine buffer tube on the gun while providing you with a Precision Stock ideal for long range and precision shooting. With all the adjustments you need to get the job done the B5 Precision Stock is the ideal solution.