Got Empty Pipets?
2-1/8" DIAMETER PIPET FILLER
Or pipettes, depending upon how you roll. These pipet fillers are chemical-resistant, 2-1/8” dia rubber with the traditional A, S & E valves. S is 7mm ID and E is 9mm ID. Squeeze A to evacuate the bulb, S to suck the liquid up, and E to release the liquid. Should be able to fill up to 25ml. Non-chemistry folks could just leave one in their bathroom and let visitors speculate about its purpose.