Belt drive upgrade for my Sieg X1 micro mill. Runs much quieter than the stock gearbox! Looks better too! Maximum measured spindle speed is ~2850, ~1750, and ~950 RPM respectively. Will definitely help with the smaller drills and endmills (smallest endmill I have is a 2-flute 3/32″)

Got the kit from http://www.mbbilici.com/index.php?route=product/product&product_id=57

They also have a version for the X2 mini mill, which is a much more popular machine.