Shooter Ready is stocking replacement lower Parts. Trying to complete that build and you sent a spring Flying or dropped a roll pin. Performing regular maintenance and just need to replace individual worn out parts. We have a selection of parts including the following: Firing pin, Firing pin retaining pins Gas Rings, Cam Pin Extractor, Extractor Spring, Extractor O Ring, Extractor Pin Ejector Roll Pin, Ejector Spring, Ejector Gas Key with Screws Charging Handle Gas Tube, Gas Tube Roll pin Gas block Ejection Port Cover, Ejection Port Cover C-Clip, Ejection Port Cover Rod, Ejection Port Cover Spring Forward Assist Roll pin, Forward Assist Spring, Forward Assist Prices vary depending on actual part.