This product is a set of 10 items for trumpets: - Slide cushion rubber: 4 pieces - Bottom cap rubber: 3 pieces - Stainless steel bottom ring: 3 pieces The slide cushion rubber is used to eliminate the "clack" sound when sliding the 1st or 3rd trigger back, but it also improves the appearance. The bottom cap rubber is used to fill the gap created when the bottom ring is inserted into the bottom cap, and it also improves the appearance. The bottom ring provides resistance to the instrument, eliminates unnecessary vibrations, and allows the sound to travel further. (Size: Outer diameter 18 x Inner diameter 8 x Thickness 1.2mm) I have put all of these together in a set, so if anyone is interested, please consider it. Thank you. m(_ _)m ⚫︎ Brass bottom ring sets are also available. It seems that the brass ones make the sound softer, while the stainless steel ones make the sound harder. ⚫︎ Although it is described as for trumpets, it can also be used for cornets, flugelhorns, etc. ⚫︎ Additional parts and individual sales are also possible. Please contact me via the comment section. ⚫︎ The bottom rings are made by punching, so there may be burrs on the edges. Please understand.