Reduced Power Buffer Spring. Sprinco collaborated with two prominent commercial ammunition manufacturers and two prominent gunsmiths to arrive at the design for the Yellow spring. It’s approximately 20% lighter than the White spring, and was the consensus choice out of 4 different evaluation samples provided to all parties. They all added in their final evaluations that if a particular gun needed a lighter spring, that the gas port should be enlarged for overall reliability. The Yellow spring is also appropriate for with low power SRTA training or SIMS Rounds for training operations.