All the best things come in small sizes. Compact rapid rootrainers are a designed for smaller scale growing with all the features of original rootrainers in a more compact module. Cell Depth 8cm (3") tray size length 24cm (9.4") width 22cm (9") Depth 9cm (3.5"). compact rapid rootrainers have fewer cells than rapid rootrainers (with 20 as opposed to 32 cells) and so are ideal for the gardener who doesn't have too much space available or perhaps doesn't want to sow large quantities of the same seeds.