This COMP Cams Cam Phaser Limiter Tool is used to help restrict Cam phaser motion for use of higher performance Camshafts in GM LT4 engines by allowing simultaneous compression of phaser springs in 2015 or newer GM LT4 engines. Combining this modification with more aggressive Camshaft profiles has resulted in large upper-RPM gains without sacrificing bottom- or mid-range performance. Complete Cam Phaser Limiter Kit sold separately.