Features Made of plastic, the surface of connectors has stripes, thus much easier for you to rotate, can be applied repeatedly, common size for most bottles, better than other connectors good educational and fun experiment and activity for school classes, home school, scouts and any other group, stimulating kids interest to physics and study You can put coloring or washing powder is added to the water in the bottle, so that the little tornado you create has different colors and bubbles, which is more interesting We provide with satisfactory service. If you have any questions about our products, you can send us an email and we will give you a satisfactory answer. Specifications: Quantity: 10 pack Material: plastic Colors: 2pcs in purple, green, red, yellow, blue Size: 49x37mm(L*D) Thickness: 5mm Package includes: 10 x Tornado Bottle Connectors NOTE You have to take the food-security ring off of your bottles to get these to catch the threads; And 2 liter soda bottles or other 2 liter bottles are suitable to use.Remove the small plastic ring on the bottle to tighten it-to prevent water leakage. Please Understand Due to manual measurement, it allows 1-2(mm) discrepancy. Please be reminded that due to lighting effects and monitor's brightness/contrast settings etc., the color tone of the website's photo and the actual item could be slightly different. Note: the picture shown is a representation of the item, you'll receive from the actual size items. Picture may appear larger on your screen. Color may vary slightly due to the color setting of each individual monitor. Please double check the sizes before purchasing.