Northrock Concrete Vibrator 2HP 4.2m 44mmMade in the USA The powerful Northrock concrete vibrators are designed to maintain optimum frequencies regardless of slump, head size, or other load factors. Features: PRO Series 2HP electric single phase motor 44mm factory sealed head 4. 2m steel braided rubber coated shaft with hardened steel liner for long life Electric motors are protected by a high strength cast aluminum housing that also dissipates potentially damaging heat. A rugged shock