Grodan Rockwool MacroPlugs feature a slit for easy insertion of rooted cuttings. Ideal for starting seeds or for growers using aeroponic clone machines. The plugs are 1.5 inch round and fit perfectly into the holes of any standard rockwool blocks, can be inserted into pebbles, or any other type of growing media. For best results, insert these MacroPlugs into a tray with individual cells. The cell will keep the plug firmly closed around the stem of your cutting. Bag contains 50 macro plugs.