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.
Pattern like Kicks and Comp N choke. About one choke tighter than others. The Pure Gold chokes are the heaviest of all choke brands made if weight is a concern. They and the Kicks chokes are my favorites but I shoot an auto.
Their new Titanium Ext. Chokes - have ordered some so cannot comment on them yet. However, I've owned the original Pure Golds and liked their performance from a pattern perspective but they were too nose heavy for me - really heavy and especially if shooting an OU.