The MM run in ring is 0.5 mm thick

the problem with using it as a performance changing tool is it advances all port timings .. this dosent always work when you are talking .5 mm .. it can work with thinner ones say .1 or .2 which makes a nice difference with about 50% of engines. When you really want to change the timing you need to change the exhaust and shulnere port timings at different measurements, ie you want the max effect of a mod. .