The knobs of the four legs of the Jacknobber®II massage tool can be used in many ways to apply deep pressure to muscular trigger points and tension. The smaller knobs provide more intense pressure while the larger knobs provide a gentler pressure. Use one knob at a time to press deeply into imbedded trigger points; use two knobs at a time on either side of the spine. Arguably this is the most satisfying and easy to use hand held massage tool available. Dimensions: 4 x 4 x 4" The Original Backnobber®II massage tool is constructed of durable, fiberglass reinforced nylon and carries a full, satisfaction guarantee. The Backnobber II is used by hooking one of its curves over a shoulder or under an arm and using its leverage to apply firm, deep pressure to knots in the muscles of the neck, shoulder, upper and lower back and to nearly any other location where muscle soreness may occur. Dimensions: 10 x 20 x 1" Colors may vary