I just installed some Rem. 3rd. blued mag. extensions on a pair of 870 Police shotguns (my twins) with 20 in. brls. The Police models don't have the ignorant dimples to deal with so it was an easy swap. The gun shop I ordered them from took about two months to find them. I tried brownells myself and through another gun shop and it was a no go. I don't blame Brownells as I am sure this policy was foisted on them by the pencil necks at Remington. I don't know where the gun shop got them but I am happy to have obtained them. Some of the delay may be that I wanted the blued rather than the parkerized version. Be sure to clean off the cosmoline both inside and out prior to installation, looks like rust on the cleaning patches don't be alarmed. Be sure and get the "kit" rather than just the extension tube. Mine came with the tube, long mag. spring, tube coupling, and clamp and screw. Al in Md.