Robert Vinson Equatone Ligatures Bb Clarinet Made of polypropylene Inverted screw placement Incredibly durable, these ligatures prove an excellent addition to a student's equipment The Robert Vinson Equatone ligatures are made from high-quality polypropylene and feature vertical rails that rest on the mouthpiece and horizontal rails that place equal tension on the reed Incredibly durable, these ligatures prove an excellent addition to a student's equipment