When it comes to a resistance rating, the letter “X” denotes a non-rating, meaning there’s either a null value or a 0 rating. IP stands for Ingress Protection, while the numbers following represent first the solid object rating, and then the water rating. So, an IPX8 rating means that the device is protected from moisture, but not solids like dust or dirt. Numbers in both slots mean the device has both solid and water protection. What’s more, the higher the numeric value the better the protection.