Intermediate Power Buffer Spring. The Hot White spring came to life as an accident that turned out to be a valuable solution for certain platforms. Sprinco did a production run of White springs where the loads came in perfectly between the design loads of the White and Blue spring, so they sat them aside and did another run of White springs to the proper load specifications. When Sprinco had some calls from customers wishing for a spring that was in between the performance of a White or Blue spring, they had them try out the discarded springs on a trial basis, and they turned out to be perfect for their needs, thus, the evolution of the Hot White spring for tuning purposes. If you are among those who are advocates of using Mil-Spec carbine springs rather than tuning to perfection, this is also a good choice in the vast majority of instances to enhance performance.