This is a Debenham, Stebbings, and Robinson capsule. It sounds very nice and is not very fussy as to diaphragm tensioning. Recommended for a first DIY. Outer plastic is Delrin. To stick it to brass, you MUST use Loctite 770 primer followed by the thinnest cyanoacrylate you can find. Even that may not work correctly. I need to work on finding a better material. Perspex is supposed to be much better, however, it is sensitive to the glues and solvents used for adhesion and cleaning.