54 - I think they are in stock and will soon be added to the inventory! But, I thought that about the new 17-4 Mountaineer Breech Plug also and it is not listed yet. I really do hope things appear in the next few days. I did send Lehigh a Treso-AMPCO nipple for their inspection and they were quite confident that this new would outlast the AMPCO. Only time will tell - I am hoping to shoot a Western DISC tomorrow with a new Lehigh 17-4 installed...