Made of polypropylene. Integral 0.2ml tubes with ultrathin sidewalls and bottoms for more uniform and efficient temperature transfer, therefore reducing PCR reaction time in most 96-well "V" bottomed thermal cyclers. They are more easily handled than single tubes. They will precisely fit standard well spacing. Caps also sold separately.- Reaction Strip with Attached Individual Caps, Flat Cap, Green, 125/cs 14-21 Days