These laboratory scissor jacks provide stable, height-adjustable support for hot plates, baths, glassware, and many other items. Positioners are constructed of rugged, chemical-resistant anodized aluminum with stainless steel operating screw. Top-plate skid pad prevents slipping. Each Positioner is precision engineered for smooth, continuous operation throughout its range. Easily set the exact height needed with the turn of a knob. Excellent side-to-side rigidity and support maximum support static load is 66 lb (30 kg).