Raymond, you can add a pistol brace but not a shoulder stock. A stock makes this a short barreled rifle and requires a $200 tax stamp. With the buffer tube that's installed you can't add a pistol brace. You would have to change buffer tube to a milspec carbine length buffer tube. Here's a link to one I'd recommend............ budsgunshop.com/product_info.php/products_id/714021927/luth+ar+carbine+buffer+tube+mil-spec.......... After that you can add any AR-15 pistol brace. I'd recommend the SB tactical sba3 brace but any would fit. Hope this helps.

Raymond, only a Brace since the barrel is less than 16 inches and it is classified as a Handgun/Pistol. Adding a true Shoulder Stock would change the classification to a Short Barreled Rife (SBR) requiring NFA registration and $200 Tax Stamp. Brace example : sb-tactical.com/product/sba3/