the SRP's are and okay piston, so are the Pro-Tru's. i don't consider either of them a top quality piston, more like middle of the road quality wise. we use them in mild to medium street/strip combo's. for the more serious stuff we use Diamond Pistons. sometimes the drawback to the typical shelf SRP and Pro-tru comes in the form of valve pocket diameter and depth and also wristpin size availability.
with Diamond i can change that stuff for a small fee to better fit the application. the overall quality and strength from Diamond is far superior overall IMO. just so you know, we handle all of the above lines so there is absolutely no bias in my reply.