The sand ring is composed of two layers of materials. The inner layer is treated cloth or paper, and the outer layer is emery cloth or sandpaper for grinding. The sand sleeve is widely used with the following characteristics:

1. Light, because of the small weight of the sand sleeve and the air swelling shaft, the portable machine used is also small in power and light in weight, so it is more convenient to use. 

2. Good working environment.

3. It can well maintain the original precision requirements by polishing the concave surface of inner hole and different radius.

4. The sand sleeve is not only used for metal polishing, but also for non-metal polishing.