Valve springs supervised by world-renowned euphonium player Steven Mead. Specifically designed for compensating euphoniums. This product is designed with a lighter tension among Mead springs. I previously purchased these here, but they didn't quite suit the instrument I use (Willson TA2900BS), so I'm offering them for sale. Based on my experience using them on my instrument, the tension is moderate, but the rebound is strong, giving a speedy return when releasing the pistons. (I'm not sure how they would feel on a Besson euphonium, I apologize.) Thank you.