Probolic-SR from MHP is a next-generation protein supplement, formulated for sustained absorption over a long period of time, up to 12 hours. In the not-too-distant past, protein powders competed with each other on a faster-absorption-is-better basis. But the Probolic-SR reflects more up-to-date knowledge that - for muscle building purposes - slower and steadier absorption is better and wastes less protein. Since most protein shakes are still oriented toward fast-absorption, knowledgeable users have to seek out the relatively few slow-release protein powders. Casein and egg white are typically the only two choices. But Probolic-SR might be a better choice since it's a protein blend specifically formulated from the ground up to be a slow, and sustained-release protein.