100mm rockwool cubes

Rockwool is made by melting a combination of rock and sand and then spinning the mixture to make fibers which are formed into different shapes and sizes. The process is very similar to making cotton candy. The shapes vary from 1"x1"x1" starter cubes up to 3"x12"x36" slabs, with many sizes in between, which makes rockwool one of the most versatile growing mediums.