1.The flyback transformer used For RECI DY13 Co2 laser power supply / laser engrave machine2.The RECI DY13 laser power supply has 2 piece / one pair flyback transformer. so you must choose 2 piece/(one pair ) for your laser power .3.Please check the install schematic diagram.4.The screw is for install fixed on the laser power box.5.If the laser engrave machine no laser beam come out . Then you need replace a new flyback transformer for the laser power.6.If the Co2 laser engrave machine laser power is weak , and it can\'t cut through any materials . Then you can adjust the laser power to maximum value. at the same time . you check the machine ampere.If the Am indicator is still less than 8 Am. Then you need replace a new flyback transformer for the laser power supply.