The Sauermann FSA6000 Floor supports made from nylon and glass fiber to absorb noise. Suitable for any use. Height can be adjusted from 3-1/2 (9cm) to 5-1/2 (14cm). The NBR O-rings placed under the blocks provide extra stability. All components are extremely wear resistant. Each kit consists of 4 floor supports shrink wrapped together (necessary to support one air conditioning unit).The quality is 8 kits.