• 👍 The holding hole is 0.315inch (8mm), that is suitable for the digital metric dial gauge.
• 👍 Quick-release lock knob releases and secures all three joints simultaneously for easy adjustments
• 👍 Twist one black knob can adjust 3 rotary joints at any direction and location.
• 👍 Two solid magnet surfaces with on/off control can provide a maximum tensile force of 176lbs (176lbs tensile force requires a metal working surface/surface with a thickness of 1.2"/30mm and above). Please tight en up the adjusting knob before using to get the powerful and stable magnet
• 👍 We are dedicated to ensuring your 100% satisfaction, If you have any issue during use, please feel free to contact us, our technical staff will reply and resolve the problem within 24 hour.