This is a Quick Disassembling Protection Ring Set Fitting for DJI Phantom 3 RC Quadcopter but can be used on different drones, like Cheerson cx-20 as you can see in the video below (check compatibility with your drone before buying it).
With these mounted on your drone you can dramatically decrease the damages to your quadcopters, expecially to propellers and motors.
You can see how to use them and how these enhance drone security in this video:
Package Content: 4 x Protection Ring, 4 x Buckle, 1 x Screw Set
|General||Type: Protection Ring|
|Dimension and Weight||Package weight: 0.215 kg|
Product size (L x W x H) : 24.5 x 14.3 x 2 cm / 9.63 x 5.62 x 0.79 inches
Package size (L x W x H): 25 x 15 x 3 cm / 9.83 x 5.90 x 1.18 inches
|Package Contents||Package Contents : 4 x Protection Ring, 4 x Buckle, 1 x Screw Set|