4 inch two faced block covers, C.A.P. 40 pack
4 inch two faced block covers, C.A.P. 40 pack. 2 Faced Block Covers reflect light back towards plants in addition to protecting them from algae growth. The white face reflects light to the plant while the black face blocks light from the media and helps with algae, mildew and pest problems. Our unique circular design prevents light passage to your blocks even when the cover shifts or moves.