Edelkies basalt 2-5 mm

then just use lawn edging stones. there are rounded ones, so you can easily accommodate vibrations. doesn’t cost much (I think obi and others 50 cents/stone) and can also be installed easily without concrete. the height for covering visibility is roughly 2x the largest stone diameter. because of the small diameter, you probably have to take at least 15mm. your mentioned 5cm is more than enough for such small stones. we have 16mm stones at about 5cm and you can’t see through them.

which type of stone is right for you will only be determined by an on-site visit. our specialist dealer offers 30 different kinds. but that’s no use to you, since you definitely have to take someone local because of transport (or it will be expensive).

I find the metal edges a bit impractical.

If you use a wider stone, you can easily run the lawn mower along it. With a metal edge, that’s not possible.

My husband can :)