Power pulleys are smaller in diameter (5-1/4") than stock pulleys.  They spin the cooling fan slower, therefore they take less energy from the engine, producing more horsepower. The drawback is that they also provide less cooling air to the cylinder heads and cylinders.  For engines that are driven off-road, racing, and/or in cold climates, they are preferred. For these engines, a sand seal is also preferred to keep the dust and sand from entering the engine case, and to keep the oil from spilling out during hard acceleration and bumpy rides.  This SACO pulley is made in the USA and has been a proven leader for decades in the VW community.  The billet aluminum pulley features laser-engraved degree numbers, and a hardened chromoly inner hub for utmost strength, best resistance to wear, and awesome looks.

Comes with a machine-in sand seal, but can be used on a stock case with a special sand-sealed collar that slips into a stock case.  Requires use of a longer pulley bolt and a special smaller belt.