Description: Replacement CO2 diffuser disc, high-density with silicon sealing ring, does not easily block. Tow sizes available : Dia. 3cm/ 1.18" or Dia. 2cm/ 0.79"; Each Pack comes with 10 piece. Helps to ensure plants receive proper amounts of CO2, improve the growth and health of your plants with sufficient CO2 supply. The CO2 diffuser disc must be screwed as tight as possible when installation. Notice: The CO2 diffuser may release big CO2 bubbles during its first 1-3 days of usage. When ceramic disc becomes saturated with water, it will then release fine CO2 bubbles, this is normal and may take up to 3 days. Specification: Material: Ceramic Diameter: 3cm/1.18 in Package Includes: 10 Piece Ceramic Disc Note: Customer satisfaction is our primary concern. If the product is somehow cracked or broken during shipping, please feel free to contact us. We will try our best to give you a satisfactory solution.