It depends on what you’re looking for.
Both 30mm and 40mm thicknesses are a good option for upgrading your garden space, and so selecting between the two should depend on preference, available budget, and the requirements of your garden.
Typically, you will find that a grass roll becomes more durable and authentic as the thickness increases. However, shorter pile grasses can be a great solution for family use or homes with pets. You’ll also notice a mixture of options in 35mm and 38mm, as an ideal mid-way compromise.