Excellent product - Carlson's Choke Tubes Remington 870/100/11-87 Magazine Extension 10 Shot

Exceptionally well built and strong, installation is extremely simple as screwing it on and off. One word of note, if you are installing this on a Remington 870 express, you will notice a couple of dimples in the end of the magazine tube. They are there to hold the new spring retainer in place. Therefore you will need to smoothen them out first before you install your new extension tube. One of the ways is to either Dremel or drill them out. I would not recommend doing that. Instead I bought a handy device from Brownells that smooths out those dimples by gently tapping what is basically a solid rod with the same dimensions down the magazine tube.