Yes, it will. You need this nut: 2OX-MZX-NCSG-M3000-12-00-1-0RD
Yes, as long as you purchase the correct, Remington 870, nut on this page: https://www.opticsplanet.com/nordic-components-shotgun-extension-tube-nut.html
The Nordic Components MXT Extension Kit, 12ga will work with a Remington 870 but you will need to use the nut at the link below.
https://www.opticsplanet.com/nordic-components-shotgun-extension-tube-nut.html?_iv_gun-model=remington-model-870
The Nordic Components MXT Extension Kit should work as long as you purchase the correct adapter. The Mossberg adapter at the link below should work with the Mossberg 940.
https://www.opticsplanet.com/nordic-components-shotgun-extension-tube-nut.html?_iv_gun-make=mossberg
The Nordic Components MXT Extension Kit will not work for the SDS Duo-Sys Force Shotgun.
The Nordic Components MXT Extension Kit will not fit a Dickinson AK212.
Yes, the Nordic Components MXT Extension Kit will work with a Benelli Supernova. You will need the Nordic Components Shotgun Extension Tube Nut located at the link below.
https://www.opticsplanet.com/nordic-components-shotgun-extension-tube-nut.html?_iv_gun-model=benelli-supernova
Yes, the Nordic Components MXT Extension Kit will work with the Fabram STF12 if you get the correct extension nut. We currently do not have this extension nut but the model number you would need is NUT-FAB-SFT12-1.
The +7 would be 0.500" past the muzzle.
These are black.