Rookhawk, I have a box in front of me now. They come in packs of five and with a 32gram (1 1/8th. ounce) Brenneke slug. They have the CIP mark which is the European proof acceptance mark to show that they do not exceed pressures for the gun for which they are intended; in this case any 12 bore gun with minimum 2 1/2" chambers that is 'in proof' and nitro proofed. Our rules of proof here in the U.K. and most of Europe don't distinguish between damascus and steel barrels provided that they are suitably proofed. There is no warning on the pack concerning choke constriction. I believe that the fins on the Brenneke slug are designed to pass through full choke anyway.
If you do manage to source some and order them make sure that they are the ones for 2 1/2" chambers as I believe that they make them for 2 3/4" as well. I have some 16 bore Brenneke slug loads by RWS and have them in both chamber lengths that I used in a drilling. Lagopus.....
