The Dust MuzzleTM Ultra (DMU8) fits all 7 to 8 inch electric and pneumatic angle grinders. It is based on the design of the original Dust Muzzle that has been used by thousands of contractors for over 19 years. It has a side-mounted exhaust port that uses the centrifugal forces created by the grinding wheel to send the dust into the vacuum hose. With this design, it needs much less vacuum suction to remove the dust from the workplace. Note: The Dust Muzzle Ultra exhaust port accepts a male fitting from a 1" hose. Most vacuums have a 1 1/2" hose. The step-down hose is a 4 1/2" x 1" ID lightweight extension that attaches to the male fitting on the vacuum hose and slides into the exhaust port of the Dust Muzzle Ultra.