The "IP" stands for "ingress protection." This measures how easily foreign bodies (like water) can enter a product's housing. The following numbers show the product's protection against dust (the first digit) and liquid (the second digit). Dust protection is rated on a scale from 0 to 6, with six being the highest level of protection. Liquid protection is placed on a scale from 0 to 9, with nine being the highest level of protection.