Drive system: Constant force spring drive with SUS 304 stainless steel instead of spiral spring ,main spring not Rolling spring;Market normally adopted the spiral spring drive system. Contact System: Axial Contact with high quality material,The axial contacts with up to three contact points, along the axis. Up to 3-pole. Release & Lock System:This product Model:DYH-1606 can be optional for Catch brake system or Permanent pull system. For this small item spring is the key component,which decides retractable mechanism and life. Our spring processing is more sophisticated than others,put us at great advantage. We make mostly all components, so we can control qualtiy,costs and leadtime. Really true manufacturer for various retractable system in China, have capacity to customise to accomodate clients products needs. We have a full range of testing equipment.include retracting life span, rated weight load,rated current load,shake -resistance... 5)We have our own design center.