The sponge is non-toxic and environmentally safe. Their color, but when exposed to air, the color becomes light yellow. This is normal. It does not affect the use of sponges. Please don’t worry Function: The sponge block has openings for easy insertion of seedlings. Ideal for hydroponics and vegetables. Hydroponic seedling sponges provide long-lasting moisture to seeds. Convenient soilless cultivation: Irrigate nutrient solution regularly without adding soil. They are suitable for most seeds, such as fruits, beans, vegetables, cereals, flowers, etc. Space saving: The sponge for hydroponic seed growth medium is very easy use. They are ideal for growing new plants from seed or hydroponics. Clean and hygienic planting saves space. Easy to use: the sponge is a good starting agent for seeds. Even if you don’t have expertise, you can use it without any problem. Size:120pcs Specification: Material: sponge p> Size: about 4820mm/1.890.79inch Weight: about 160g Function: used for seed