Gear driven disk. Stable and solid. Specially designed filter disk allow different glass thickness for unmounted filters. From 0.7mm to 5mm. Motor moved to a corner to increase the work area. Increased the precision for filter location. Support USB port and powered by USB when connected with computer. Support the 4PIN QHY CFW socket on QHY11,QHY21/22/23 and InterCam series camera. Support the 2pin socket with QHY9(Need external power supply). Open Source Firmware, Arduino compatible QHYCFW2-S: Small size. Support five 36mm umounted filter.Thickness is only 15.5mm. It also support the six 1.25inch unmounted filter with an optional disk(need special order). The weight of QHYCFW2-S is 365g.