XL tyres are reinforced tyres designed for heavier vehicles, which explains the meaning of the abbreviation "extra load".They are usually used by SUVs, large sedans, vans and electric cars. The reinforcement makes the tyre perform better under heavy loads.Whether it is an XL tyre is not directly dependent on the weight index, although most XL tyres have a weight index above 90 (>600 kg).
Maxxis Premitra Snow WP6 is made in 32 sizes, which of them 24 are made in the XL specification :