Hybrid bikes as the name suggests are a blend of a road bike and a mountain bike. The fit is a little more precise than a mountain bike, and a little less than a road bike, so you do see a mixture of t-shirt style sizing and measurements…
Mountain Bikes tend to use the T-Shirt sizing of S, M, L etc. or will have the seat tube measurement in INCHES. Why mountain bikes are inches and road bikes are CM who knows, but the part of the frame being measured is the same. As a rule…