played by a single drummer. The bottoms of the shells are open and beveled to project the sound of the drum forward. Double-ply PET film heads are typically used for increased sound projection and durability. They are typically played with wooden- or aluminum-shafted mallets that have disc-shaped heads made of nylon. Mallets with felt or fleece heads, drum sticks, drum brushes, and other implements are occasionally used to achieve different timbres. The playing technique used for multi-tenors is somewhat different from that of a snare drum, and more like that of a timpani because the drumhead is struck closer to the edge instead of in the center. This creates a sound with more overtones, as opposed to striking the drumhead in the center, which produces a very short, dull sound with few overtones that is considered undesirable for multi-tenors. A full-size set of tenors consists of 10, 12, 13, and toms arranged in an arc, often with an additional one or two smaller (6 or 8-inch) toms called "gock", "shot", or "spock" drums inside of the arc. Because a full-sized set of tenors with a carrier can exceed 55 pounds (recently the Dynasty Quints, thought of as one of the heaviest sets, weighed in at 32 lbs. without a carrier) smaller and lighter versions of tenors outfitted with 8, 10, 12, and toms are often used by lines with smaller or younger players. All multi-tenors based on the four-drum configuration are called quads despite the fact that there may be a total of five or six drums counting the gock drums. Sets with one gock drum are called quints, and sets with two gock drums are called sextets, "squints", hexes, or sixpacks. To produce different sounds between spock drums with the same diameter, the head type, shell depth, and/or tuning between the two drums may vary. A common name for all multi-tenors is simply, 'Tenors'. Tenor drums have often been compared to the Latin percussion timbales, as many musicians, including Tito Puente use a setup similar to modern marching tenors. Lines of as few as 1 or 2 tenor drummers are common in high schools and junior high schools. Many large college marching bands have 5 or more. Most drum corps consider 4 or 5 tenors to be optimal. The modern multi-tenors evolved from horizontally mounted dual single-headed bass drums first used by the Boston Crusaders Drum and Bugle Corps