In the past, the floor exercise event was executed on the bare floor or mats such as wrestling mats. Today, the floor event occurs on a carpeted 12m × 12m square, usually consisting of hard foam over a layer of plywood, which is supported by springs or foam blocks generally called a "spring" floor. This provides a firm surface that provides extra bounce or spring when compressed, allowing gymnasts to achieve greater height and a softer landing after the composed skill. Gymnasts perform a choreographed routine up to 90 seconds in the floor exercise event; Depending on the level, they may choose their own, or, if known as a "compulsory gymnast," default music must be played. In some gymnastic associations such as United States Association of Gymnastic Clubs (USAIGC), gymnasts are allowed to have vocals in their music but at USA Gymnastics competitions a large deduction is taken from the score for having vocals in the music. The routine should consist of tumbling lines, series of jumps, leaps, dance elements, acrobatic skills, and turns, or piviots, on one foot. A gymnast can perform up to four tumbling lines that usually includes at least one flight element without hand support. Each level of gymnastics requires the athlete to perform a different number of tumbling passes. In level 7 in the United States, a gymnast is required to do 2–3, and in levels 8–10, at least 3–4 tumbling passes are required.