Benelli M1 super 90 flushed mag extension tube

[nyc71]

I'm picking up a M1 tomorrow, is this the right mag extension for a 21" barrel?

https://www.benelliparts.net/products/benelli-m1-m2-super-black-eagle-sbe-and-super-black-eagle-2-sbeii-6-round-magazine-kit-12-gauge?variant=43039267553518

Which ones out there are proven to work & are flushed with 21" barrel?

Thanks in advance 

[Steve Rose]

I expect the 6 round tube will extend past the end of your 21" barrel.  The Nordic +5B tube  is designed to to match the 21" length and Nordic products have a strong following in the shotgun circles.

[nyc71]

21 hours ago, Steve Rose said:

I expect the 6 round tube will extend past the end of your 21" barrel.  The Nordic +5B tube  is designed to to match the 21" length and Nordic products have a strong following in the shotgun circles.

Thanks for the link