This is a gas disk for fish tank and aquarium. High quality gravel material, solid and durable. Reusable and easy to clean. Grade nano material, ensures smaller bubbles and better dissolved oxygen, make fishes living environment more comfortable and natural. It is also a wonderful tool for increasing oxygen and renew fish tank air. Features: High quality gravel material, solid and durable. Simple design, easy to use. Eco-friendly: Reusable and washable easy to clean. A wonderful tool for increasing oxygen and renew fish tank air. Suitable for low press pump, smaller bubbles slowly rise up, bringing a fantastic visual enjoyment. Grade nano material, ensures smaller bubbles and better dissolved oxygen, make fishes living environment more comfortable and natural. Specification: Condition: Brand new Material: Gravel Color: White Size: Approx. C-50 7 x 2.5cm/ 2.8 x 1.0in C-100 13 x 2.5cm/ 5.1 x 1.0in C-150 15.6 x 2.5cm/ 6.1 x 1.0in C-200 22 x 2.5cm/ 8.7 x 1.0in Package list: 1 * Nano Bubble Disk Note: Please allow 1-3cm error due to manual measurement and make sure you do not mind before ordering. Please understand that colors may exist chromatic aberration as the different placement of pictures. .