1. Circular cylinder equipped with valve
2. Some models have built-in speed control valves
3. Cylinder with valve, the speed is easier to adjust
4. With magnetic switch (CDVJ series: CDVJ5, CDVJ3, CDVM series: CDVM5, CDVM5K, CDVM3, CDVM3K, CDV3 series: CDV3, CDV3K, CDVS1 series: CDVS1, CDVS1K)