The floor event occurs on a carpeted square, called a "spring floor", consisting of hard foam over a layer of plywood, which is supported by springs or foam blocks. This provides a firm surface that will respond with force when compressed, allowing gymnasts to achieve extra height and a softer landing than would be possible on a regular floor. A series of tumbling passes are performed to demonstrate flexibility, strength, balance, and power. The gymnast must also show non-acrobatic skills, including circles, scales, and press handstands. Men's floor routines usually have multiple passes that will total from 60 to 70 seconds, and men perform without music (unlike women gymnasts). Rules require that gymnasts touch each corner of the floor at least once during their routine. Female gymnasts perform a 90-second choreographed routine to instrumental music on the same spring floor used by male gymnasts. Female routines consist of tumbling passes, a series of jumps, several dance elements, acrobatic skill elements, and turns. Elite gymnasts may perform up to four tumbling passes, each of which includes three or more skills.