Material: High quality acrylic
1.Place the speed dial on the turntable and turn on themachine.
2. Turn on the incandescent lamp，close to speed dial about 5-10 cm.
3. Observed the corresponding 33.3/45 speed stripe on the speed dial .
If the fringes are stable and do not move, the speed is correct.
If the stripe is in the forward state, the speed is too fast.
If the stripe is in the retracted state, the speed is slow.
4.Can measure overhang.
5. Can be used for light record clamp.