ToneKnob

The ToneKnob is a super heavyweight neck screw that replaces the existing neck screw on your saxophone. At 2.4oz, it's far heavier than the other heavyweight neck screws on the market, and the extra weight is what makes the ToneKnob far more effective than the competition. Excess vibrations are absorbed by the ToneKnob making the instrument perform much more efficiently. In addition to added volume and richer tone, most players notice the response of the saxophone is greatly improved making for crisper articulation, easier altissimo, and just a generally more enjoyable experience. 

These are designed to fit the most popular brands of saxophone and are available in the four different thread sizes used by all manufacturers; 

M4x.7  Yamaha, Keilwerth, Buffet, Antigua, Selmer AS42 & TS44 series

M4x.75  Selmer, Yanagisawa, Jupiter

M4x.8 Cannonball, P. Mauriat, Eastman, (most Taiwan brands)

8/32 (Vintage American brands) Conn, King, Buescher, Martin