Many prototypes have been sidelined along the way that were all different combinations of high mass, low mass, different types of mass distrubution, mass based on contact points, etc. There have been lots of different alloys, shapes, and sizes, all play tested to figure out what is the best combination for ideal sound quality and tone feel. Designs that have something special will likely be added to the store at some point.
Here is an example of custom key risers made with wood. Epoxy risers and cork risers are both available, as well.
Several different metal bore insert designs for hard rubber tenor mouthpieces have been made in collaboration with SK Mouthpieces. Playing a hybrid metal/HR piece is a lot of fun!