Remington sends out many of their shotguns and weapons based on shotguns with two dimples in the magazine tube. This was a manufacturing shortcut for Remington, but the effect is that it prevents installation of any magazine extension on the weapon. So if your Remington has dimples, no matter whether you want to add a Suarez Plus one, or any other company's extensions, it will not work right, and you will not be able to add any more rounds than the four that fit in the dimpled magazine.
Solutions? Remove the dimples. Many will try to do this at home with varying success, often damaging the magazine tube or leaving unsightly holes in the tube. The problem is that if you mess it up, it creates far more problems than sending your 870 to us for work. A far better solution is to send the 870 to us for dimple removal. Our gunsmiths have the tooling and expertise to make the dimples go away and allow you to mount any magazine extension you wish on your 870.