These remove 99.9% moisture and deliver extremely dry compressed air. For best results, they must be used in conjunction with filters to prevent any materials or oil from entering the chamber (filter to be immediately ahead of the dryer). When the desiccant has changed from dark blue to a pink colour (between 5-20 hours), the beads must be replaced or possibly regenerated in a drying oven at 135°C (275°F) until it turns dark blue again. The 3/8" body (125 ml) is rated for a maximum 150 psi (105scfm) and the 1/2" body for a maximum 250-300 psi.