No, all 21 mower blades are not the same. There are a variety of different types and sizes of mower blades available on the market, designed to suit different types of lawns and grasses. The most common blade sizes are 16 inches, 18 inches and 21 inches, but there are also specialist blades available in other sizes. The type of grass you have will dictate which size and type of blade is best suited – for example, a coarse-bladed mower will be better at cutting long grass than a fine-bladed one. It's important to choose the right blade for your lawn to ensure a neat and tidy finish.