This is an Aqua Craft Grim Racer Precision Metal Prop Balancer. FEATURES: * Three thumb-screw adjusters * Bubble level centered in wide stance base * Balances almost all metal props * Made of extruded aluminum. INCLUDES: One prop balancer with instruction sheet, O-ring keepers, .187" 1/8" 3/16" and 1/4" shafts. SPECS: * Length: 6.3" (155mm) * Width: 3" (75mm) * Height: 2.25" (63mm). REQUIRES: * Dust mask * Eye protection * Small round file * Small flat file * 220 Wet/Dry sandpaper * Scratch pad (red) * Felt tip pen