103A is a mysterious number often used to describe the hardness of a skateboard wheel. The hardness of skateboard wheels are measured using the Shore test. The A refers to the Shore A scale, which is designed for measuring the hardness of rubber and softer plastics.

The catch is that the Shore A scale only goes to 100. Shore hardness is measured using a durometer. The hardness value is determined by the amount of penetration by the durometer into the material being tested. If the material is completely penetrated, the reading is "0". If there is no penetration at all, the reading is "100".

In other words, it's impossible to have a reading higher than 100A. Wheel manufacturers use numbers like 101A and 104A, but they aren't actual figures, just marketing hype. Their wheels may be slightly harder than everyone else's 99A, but no matter how much harder they actually are, they can't be rated higher than 100 (at least on the Shore A scale).