Aquarium Planted Tank DIY CO2 System D301 CO2 Generator Feature: Promoting plants growing, easy to set up, low cost, safe. With 2 air-pipe locks on the bottle cap, prevent the air-pipe get loose. Specialized pressure gauge, safe area and scale can be seen clearly. The complete DIY CO2 kit combo for planted aquarium. You can built up your CO2 system within 15 mins. This bottle cap is very well suitable to be DIY CO2 system 's accessory that the size fits common PET plastic bottle. Attention: The bottle have to use c arbonated beverage bottle, do not use pulpy, green tea, mineral water bottles, etc. Trimming valve regulation avoid by sudden big or small, do not suddenly turn up, after immediately shut down again, so as not to cause abnormal pressure to the bottle. Make sure carefully observe the direction of the parts before assembly. The usual wrong handle way will cause abnormal react ion components as follow: the contrary direction of the check valve and fine-tuning in the direct. Product Attributes: Model: D301 Model Thumbnail Vavle Pressure Gage Cover Tube D201 D301 D501 Package Include: 1x Pro needle valve 1x Pressure gauge 1x Extra tube 2x Bottle caps with tubes 2x Tube holder If you want to set up th e Generator ,you need (not included in the product): 1x 200g of citric acid 1x 200g baking soda powder 2 x Soft drink bottle (recomended 2L bottle) Note: 2.Due to the light and screen difference, the item 's color may be slightly different from the pictures. Please understand. Make sure you don 't mind before you bid. 3.Please allow 1-5mm differences due to manual measurement. How you to set up