PCR tubes are small tubes made of high-quality virgin polypropylene with a conical bottom and snap-cap lead. They have uniform thin walls to facilitate efficient heat transfer to the sample. These tubes are autoclavable and work well with most thermal cyclers. A cuvette is a piece of laboratory equipment that is intended to hold samples for spectroscopic analysis. Cuvettes are made from glass, plastic, or optical-grade quartz. Plastic cuvettes have the advantage of being less expensive and disposable and are often used in fast spectroscopic assays.