A built-in silencer muffles noise as you work with this economical dual-action sander It's a quality sander used for feather edging, metal preparation, and finish work on body filler Its dual-action pad motion produces swirl-free finishes Low vibration Balanced ball bearing construction Adjustable built-in regulator for positive speed control 6 Dual-Action Quiet Air Random Orbital Sander - 311A .