New pair of Comp Cams checker springs tool.  Checker springs are a tool used to replace the intake and exhaust valve spring for 1 cylinder to check PTV (piston to valve clearance).  These allow you to depress the valve by hand to get the measurement.  Checking PTV is one of the most important measurements to take when changing your camshaft, especially on motors with flat top pistons with no valve reliefs (such as nearly all of the LS based motors).  If you have too little PTV, you chance the valve hitting the piston.   To use the checker springs, you rotate the motor so that your valve is at the closest point to the piston, then using a dial indicator, you push the valve down with your finger to get the measurement.  That measurement is your PTV clearance.  If it all checks out within tolerance, you put your valve springs back on and continue with engine assembly.  If your PTV is too small, you can either use thicker head gaskets, use an adjustable timing set to advance/retard the cam (that changes PTV), have the pistons eyebrowed, or some other options.

These checker springs are 2" tall x .875" wide, and work on the LS motors and other motors with installed height less than 2".  2 springs are included in this kit.