New Harmony Carbon Fiber Cello/Bass Endpin Rod Only. 24” Long, 10mm diameter with Carbide Tip. Rubber Cap Included. Carbide tips stay sharp and easy to sharpen. Tip is also replaceable. Endpins absorb energy generated by bowing, and it is logical that a heavy steel end pin will absorb more energy than a carbon fiber end pin. Carbon fiber end pins have a positive effect on the sound produced by a cello and double bass.