Originating in Holland the Rockwool Technique of growing is extremely popular. Blooms Hydroponics Birmingham supply Rockwool in slabs and cubes, depending on the type of growing method you undertake.
Rockwool has been around for decades and is well-known in the hydroponic growing community. It is made by melting rock and spinning it into extremely thin and long fibers, similar to fiberglass. They take these fibers and press them into cubes of varying sizes.