This kit includes everything you need to convert your Crosman 1377 or 1322 into a custom carbine. The kit includes a 4140 steel machined black-oxide coated adapter, 3d printed buffer tube, and bolt. The stock can quickly be adjusted from an 11 to 14-3/4 length-of-pull. The buffer tube is 3d printed in ASA. It is attached to the airgun with a machined steel adapter and reinforced with a -20 X 6inch bolt. It is made to MILSPEC dimensions. We highly recommend Magpul buttstocks for this extension tube, but it is compatible with any MILSPEC AR adjustable buttstock. This is compatible with a stock 2240 or 2240XL. Note that you will no longer be able to use the stock iron sights with this stock. If you have a steel breech I recommend you use a scope with tall scope rings. PLEASE NOTE: If you cannot get the screws to align with the screw holes in the adapter you may need to remove the buttstock and loosen the long bolt that goes through the stock tube, reinsert the steel adapter, install the stock screws, then retighten the long bolt. This item will not work with power adjusters or rear cocking handles!