Standard compression systemcompression systems are required if you are using threadless forks a threadless headset they replace the 2 lock nuts on standard threaded forks and let you compress and tune your threadless headset this clamp has more clamping power than some of the others on the marketthe apex pro scs is 78mm in heightapex scs gama weighs 247gms the lightest and on the marketincludes3x m8 bolts 1 x m6 bolt 1 x volcano centre cap 1 x alloyshim