I have a set for my Kolar T/A MAX. Very nice chokes. I especially like the .020 for 16 and the .030 for handicap. They are ported, or at least the ones I have are. They do add about 1 inch plus to the overall length of the barrel. The constriction is gradual on their Kolar chokes, not abrupt. Nice even patterns are thrown with a hot core so if you are on, you can smoke birds. Somewhat like a Muller choke in that hot core regard.
Hope this helps.
Art