Application notes for all pump shotguns:  many tactical type pump model shotguns comes with a 8 plus 1 capacity, and while they will hold 8 shot shells in the tube, they will not hold 8 slugs in the tube.  Use the +1 tube extension to get 8 slugs in the tube for 8 plus 1 slug capacity.

Nordic extension tube assembly length (includes barrel nut in measurement):

Winchester SX2/SX3/Browning Gold +2 - 5.76"

Winchester SX2/SX3/Browning Gold +5 - 11.60"

Winchester SX2/SX3/Browning Gold +8 - 19.82"

Benelli Nova/Beretta Extrema +1 - 3.21"

Benelli Nova/Beretta Extrema +2 - 5.89"

Benelli Nova/Beretta Extrema +3 - 8.42"

Benelli Nova/Beretta Extrema +4 - 10.19"

Benelli Nova/Beretta Extrema +5 - 11.73"

Benelli M1/M2/SBE +4 - 10.47"

Benelli M1/M2/SBE +5 - 12.01"

Benelli M1/M2/SBE +7 - 17.62"

Benelli M1/M2/SBE +8 - 20.23"

Benelli M4 +2 - 5.89"

Remington 870/1100/11-87 +4 - 10.05"

Remington 870/1100/11-87 +5 - 11.59"

Remington 870/1100/11-87 +7 - 17.20"

Remington 870/1100/11-87 +8 - 19.81"

Mossberg 590/835 +1 - 3.28"

Mossberg 590/835 +2 - 5.96"

Mossberg 590/835 +3 - 8.49"

Mossberg 590/835 +4 - 10.26"

Mossberg 590/835 +5 - 11.80"