transparent When the socket inside is stuck , please use a paper clip to from the input end to the output end Package content : 10 pcs x air check for The check for is suitable for common aquarium air pumps Please do not use with CO2 systems One-way check for for aquariums and fish tanks Stomatal diameter : 0.15 " / 4mm ; total size : 2.16 " x 0.58 " / 5.5 x 1.5 for cm ( LengthxMax.D Protect your by the aquarium water from anti-siphoning during power outages, Manufacturer: Watreketal