Thermaflow mobile hydraulic coolers from STAC Inc. serve as the heart of a truck hydraulic system. The all-in-one unit provides a reservoir, cooling, valving and filtration for hydraulic oil in one package, mounted on either a frame rail or behind the cab. They come with a hydraulic or electric fan and a relief or control valve. As the hydraulic oil in a system is used, it begins to heat up, slowly deteriorating the life of the system. The unit allows a smooth-flowing system using very little hydraulic oil, reducing the weight on the truck. Six models for almost any sized bulk delivery vehicle are available. 800/334-7699; www.thermaflow.com.