This magazine extension made by S&J hardware These are of 2 peice construction wich consist of the tube and nut  have the bayonet step machined in and silver soldered to the end just like the Remington 870 factory extensions, They do not have the Ring for the magazine clamp screw and have a straight body allowing you to use a magazine clamp of your choice or to use the S&J Bayonet lug/ magazine clamp.

 They are made of chrome moly steel tubing and parkerized to match your Remington 870.