These are the standard three valve bulbs that you are most likely use to, but in four new exciting colors. Each filler is made of 100% natural rubber and can pipet up to 50 mL's. They have a 1/4" diameter opening to fit the majority of pipet's on the market today. Natural rubber pipet fillers are excellent for transferring corrosive, toxic or sterile liquids safely. For more chemical resistant needs try our Silicone Pipet Filler. Made in Germany.