Convenient 6 gram packet or 5.3 oz (150 gram) tube.  The small size is best suited to residential-scale housings.  Use the 5.3 oz tube for Max Flow ("Big Blue") housings. The small packet is similar in size to a condiment packet at a fast food restaurant.  The 5.3 oz tube is about as big as a medium-sized tube of toothpaste.

Use this Dow Corning Molykote 111 food-grade lubricant on housing o-rings each time you change your filters. Simply unscrew the housing, remove the oring using a toothpick or other means, being careful not to pierce or cut the oring.  Gently wash the oring with dish soap and water, and pat it dry.  Inspect for damage.  Put a dab of lubricant between your thumb and index finger, and spread it on all surfaces of the oring.  Clean the oring groove if necessary, and place the oring back in its groove.  Tighten the housing by hand, with just an 1/8 turn nudge with the housing wrench if necessary.  If the housing leaks, replace the oring - DO NOT use brute force with the wrench to get the housing to seal as permanent damage to the housing will result.   Do not use petroleum jelly ("Vaseline") to lubricate o-rings.