Perflourinated polyether oxygen grease. Non toxic with white cream appearance.The various elastomer seals in the O2ptima™ rebreather should be lubricated. The recommended lubricant is CHRISTO-LUBE MCG-111 manufactured by Lubrication-Technology. MCG-111 synthetic lubricant is chemically inert, oxygen-compatible, non-migrating, odorless, non-toxic, and non-flammable. MCG-111 operates over a wide temperature range and exhibits great compatibility with rebreather plastics and elastomer O-ring seals. 2 OZ in one tube, or 1/2 oz in a small box.