Satellite Industries offers 250- or 300-gallon holding tanks made with interlocking stacking posts, recessed ports and connections, two internal pillars for added strength, molded fittings, thickened corners for extended wear, and end-to-end fittings for linking tanks. They are available in gray or a neutral translucent color, a height of 16.35 inches, width of 60 inches, length of 95 inches, and weight of 136.3 pounds. 800-328-3332; www.satelliteindustries.com.