The tiles are 500x500. You basically lay a North South and East West cross in the middle of the room so you can visualise where your cuts/ joint lines will be. You may choose to centre a joint on your French doors for example and half way across the depth of your shed. Or centre on the French doors with a full tile on your way in leaving whatever the cut is behind your games on the far wall
The dappled finish is better than the grippier/ non slip/ gym style raised dots.
You can hire a guillotine to cut them, but I used an electric jigsaw. Takes maybe 20 to 30 seconds per tile to cut. Very easy. Just lay them. No glue, membrane or underlay required.
You leave an expansion gap of about 5mm around the perimeter. You do not notice this once down as the tiles 7mm thick. I have put silicone in some of my expansion gaps. I do think they might be a waste of time actually as I have never noticed any expansion, so use a smaller gap these days
There are door threshold "ramps" you can buy If you want
I have only ever bought direct. Ecotile often has a half-price special offer on something. I have bought all mine, spread over 8 years, with the benefit of this. It may be end of a batch. Or a custom colour they are left with (used in my gym), or a slow selling colour.
My pinshed has the hidden join version called the 500/6 that sadly is no longer produced by ecotile - but other companies make them. They are much fiddlier to fit, but you get a straight line bevelled join rather than the jigsaw. However 99 per cent of these things you see in gyms/ garages are the classic and original jigsaw style and most folk will neither notice nor care
https://r-tekmanufacturingltd.com/r-tile-excel-hidden-join-flooring/
You are welcome to come over to have a look and have a go at cutting one when plague rules allow