The old style biscuit probably averaged 1% speed loss compared to a dropaway rest. There are factors that would effect this number. Using three inch straight fletch feathers the speed loss would be hard to measure. The state of tune of the bow will also have an effect on what will be lost. I usually tie in a nockpoint with a piece of bowstring and the difference in speed between using a brass nockpoint and one made of bowstring material more than compensates for any loss from the biscuit. The new B-2 biscuit shows no speed loss compared to a prong style rest. Good luck hunting!