Product Specification: 100% brand new and high quality Material: Plastic Features: Great one way check valve for aquarium air pump. Durable and easy to install. Fit standard aquarium air pipe of 4mm inner diameter. Efficient, Effective protection for your pump Non Return anti syphon valves to protect your electrical equipment. (air pumps etc) Package included: 1 Set (10 pcs) x One Way Check Valves