These cam arms were specifically designed as a Z1 Turbo upgraded cam arm set. This a new proven and tested design that is prefered by Z1 Turbo tuners. These arms have a large hump on the back that creates more engagement and more load when the turbo needs it. Available in a 72 gram base with the capability of adding 42 grams per arm for adjustment. This design allows the option of adding large quantity of weight to three different areas on both sides of the cam arm to create the shifting characteristics you desire. Each arm is supplied with tungsten and steel washers that can be used in various combinations to achieve the desired operating RPM. The SUPERTIPS will fit the stock ZI primary but will require a .06 spider shim to be installed(dependent on year of production). The tungsten washers included in the kit weigh 7 grams each. There is no other arm on the market that allows this wide range of adjustment.