Krytox GPL 205g0 (Grade 0) is a thick semi-fluid grease. Each vial of lubricant contains approximately 2ml of Krytox GPL 205g0 (Grade 0). 2ml of lubricant is enough to cover ~150 switches but of course this is highly dependent on the amount of lube you use per switch.
Lubing your switches offers both a different feel as well as an improved sound signature.
This particular variant of lubricant is not recommended for tactile switches, it is recommended for linear switches.
For a guide please see Top Clack's guide