Plywood in 4mm, 6mm, 9mm, 12mm, 15mm, 18mm and 25mm, in the standard eight foot by four foot sheet.
Commercial plywood is 240 rufiyaa in 6mm, 430 in 12mm and 620 in 18mm. Marine plywood is 1,150 in 18mm, and the difference is entirely in the glue and the number of voids in the core.
Here is the part worth reading. Commercial ply uses a glue that softens with moisture. It is perfectly good for a wardrobe carcass in a dry bedroom, a shop fitting or anything that will never get wet. Marine ply uses a boil proof glue and a core with no voids, and it is what a bathroom vanity, a kitchen sink unit or anything on a boat has to be made from. A commercial ply vanity in a Malé bathroom delaminates in about two years, and the carpenter gets the blame rather than whoever sold the board.
We will show you the difference on a cut edge and we will not sell you marine ply where you do not need it. About a third of what is sold in this country as marine ply is not, so ask any supplier to cut a corner off and look at the core.