A knurled thumbwheel operates a rack-and-pinion plunger that controls the syringe. One-hand operation enables the user to fill or deliver with remarkable accuracy since the rack and pinion performs so smoothly and precisely. Rapid-release lever allows for quick emptying. The filler has a tapered socket that accepts the pipet. If you wish to fill different size pipets you must acquire different size pipet fillers. The pipet fillers are color-coded for use with different sizes of pipets. Polyethylene with silicone rubber ring seals. Easy to disassemble for cleaning.