748 valves are smaller and 996 larger, you need 916 valves for a 916, ST4 and Monster S4 use the same engine but use different cylinder heads which are slanted (for better clearance in the frame) on the intake side, so the intake valves are shorter but I think the exhaust valves are probably the same?Someone else will have to confirm, but I believe all 748's and 916's use the same valves EXCEPT the most limited models--SPS, R, and RS. Not sure about the 996's. Those might be bigger.