I have a 870 21" and a 1100 LT-20 21" both in 20ga and both do very well with the RSFT tube and LB #6's. I've tried several other tubes and the RSFT, the Carlson's .575 and the Trulock Heavy 7 chokes seem to be what my guns like better so far. They'll average 135-145 in the 10"er at 40yds consistently. I'll agree with DBell as too the 20 yard patterns, you better be holding dead on.