20mm

Consider you use 20mm Size is an important factor when considering your paving.  Larger slabs with less lines to draw the eye can make a small space appear larger.

If you use smaller slabs they may be easier to handle than the larger sizes, which may be an important consideration if you want to complete the job without help.

Conversley, the larger sized paving slabs will need less grouting because there won't be as many gaps.

If you're sizing pebbles and chippings 20mm are best for pot toppers and borders.