Features: 100% brand new and high quality. CO2 system is designed for low cost planted tank use Easily set up/low cost/excellent quality This bottle cap is very well suitable to be DIY Co2 system's accessory that the size fits common PET plastic bottle. The composition is used as special high quality plastic for issuing great resistibility of rub, so it can be used for a long time. As for the another advantage of specific, we attached the great quality plastic O ring inside of the cap to prevent missing the Co2. Easy set up, excellent disign. It's worth to try and using it. Specifications: Material: ABS Color: (shown as the pictures) Size: (As picture shows) Inside diameter: Approx 27.5mm/1.08" Quantity:1PC (No retail package) Note: Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!!! Compare the detail sizes with yours, please allow 1-4CM differs due to manual measurement, thanks! Package includes: 1PC X Bottle Cap