This is a custom-made Bob Reeves C2J for flugelhorn with a backbore shank. I ordered it to gain volume without sacrificing range when playing flugelhorn in British brass bands, etc., as it has more volume than the Bob Reeves HF cup while keeping the cup diameter small. Because it has a backbore shank, it cannot be used on a trumpet. The rim and cup are both 40, but there is a slight step between the rim and the cup. It is unknown whether they are still accepting custom shank orders. I have many other items for sale, so please check them out if you'd like. #TPY's list of items for sale is here Type...Flugelhorn Accessories/Parts...Mouthpiece