Made of polypropylene
Caps are available either with or without a silicone washer between the cap and the tube to ensure a positive leakproof seal at all temperatures. Closures and tubes are both manufactured of polypropylene, providing the same coefficient of expansion. The cap features a long skirt and a superfast thread design allowing it to be removed or screwed on with a single turn. Autoclavable.
THESE SILICONE WASHER CAPS WILL GUARANTEE A POSITIVE LEAKPROOF SEAL AT ALL TEMPERATURES