Adjustable volume models allow five of the laboratory's most frequently-used volumes to be set-up and stored for routine use and later recall. Other volume settings can be selected at precise increments throughout the pipette's range. A low-force, form-fitting plunger manually controls aspiration and dispensing speeds with minimal effort. This is especially important for samples containing cells with fragile membranes that can be easily disrupted, or fluids that tend to bubble. Accuracy: +/-0.8 percent at 200 microliter, +/-0.8 percent at 100 microliter and +/-2.5 percent at 20 microliter. Precision: 0.15 percent at 200 microliter, 0.25 percent at 100 microliter and 1 percent at 20 microliter.