In this post from several years ago, I discussed the process of changing rotor stops, or “bumpers” as they are sometimes called. It’s a fairly simple, if a little time consuming, process. In the article I mentioned purchasing my rotor stop material from Osmun music. Along with Osmun, there are many other great horn shops out there who sell the material in varying diameters, hardness (duro), and materials. However, another place to check out is the O-Ring Store, a wholesale retailer based in Idaho. Their O-Ring cord stock can be purchased by the foot, in Neoprene, Silicone, Buna-N, among other materials. It is extremely economical to buy rotor stop material this way, as long as you know the diameter you need for your horn, and the type of material you want.
James Boldin's Horn World 
James,
How do you determine what size and type of material that should be used? I have an N series 8D. Where can I find the required specs and what material do you recommend?
I am a retired band director returning to playing my horn. I have several private students and I use many of your published materials for my warmups and exercises. I am very grateful. They have aided my own growth as well as given me a solid and reliable pedagogy to pass on to my students.
Thank you
Wayne Kitt
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Hi Wayne,
Thanks for visiting my site! Osmun Music (http://www.osmun.com/care/parts/horn/buna-rubber-rotor-stops.html) lists the following sizes for rotor stops: “Use .210″ for Paxmans, Holtons, Schmids, and most other horns and trombones. Offered in standard 50 duro and extra-soft 40 duro. Our .188 stock fits Conns, usually with no trimming. Available in 70 duro only. For a softer feel use .210 in 50 or 40 duro. .250″ is needed for some Alexander change valves.”
I really like the feel of the silicone valve stops. They have just enough cushion and not too much bounce.
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