Mastercool is the leading manufacturer of professional quality A/C manifold gauge sets. Our manifold gauge sets are constructed of the finest materials and machined with precision to the highest quality standards. At Mastercool, every manifold we build is built to last. • Anti-flutter gauges smooth out needle movement • Yellow hose includes shut-off valve • Piston type free-floating valves reduce o-ring wear • Extra access port for vacuum line • Gauges can be recalibrated to maintain accuracy • Inner nylon layer hoses meet EPA, SAE and UL standards