Check the listing for details. THREE ARCHERS Archery Bow Tuning and Mounting String Level Combo Kit Orange. Color: orange, Condition: New. Listed at 14.75 USD. FUNCTION: checks vertical and horizontal position of bow for nock and sight. EASY TO USE: Just hang the string level on the string or arrow and see whether the air bubble is between the lines. MATERIAL: Bubble level, ABS material, sturdy and durable.