According to the site it has an anti-slip rating of R11, but it's a smoother surface than some of the samples I had seen.
For a couple of reasons it doesn't really bother me if it's slightly slippery when wet (hard to say for sure until it's down). For one it's in the back garden so not having to walk over it to get in/out of the house. For two it should be easier to clean if I need to.
I have a family member with honed sandstone, that is really slippery when it's been raining, and you need to walk across it to get out of the house.
These are the two I was picking between. I went for the left one but it's definitely a smoother surface than the right one. Side note the samples also make good coasters!