The Specialty Archery Super Ball Peep is the most versatile peep ever designed. The peep opening is 3/16". The "Super Ball Peep" is designed to accept all of the Super Peep 1/8" apertures, clarifiers, and verifiers. Use of the dual aperture wrench is recommended for insertion of optional apertures, verifiers, and clarifiers. The 37 degree peep is generally used on bows 40" and shorter. CAUTION: High powered bows create a great amount of vibration. This may loosen verifiers, clarifiers and apertures over time. Tighten your apertures before each use. If you hear a buzzing sound, this indicates a loose aperture. You may use a drop of the blue Loctite or Vibra-Tite VC 3 to help hold the apertures in place.