PP. Good resistance to stress cracking and tolerant of many organic chemicals and PP tanks can be autoclaved. Very versatile at a much lower cost that stainless steel tanks. Supplied with cover and can be modified with factory-installed spigot. 21CFR177.1520 / USPVI / autoclavable. PP. Good resistance to stress cracking and tolerant of many organic chemicals and PP tanks can be autoclaved. Very versatile at a much lower cost that stainless steel tanks. Supplied with cover and can be modified with factory-installed spigot. 21CFR177.1520 / USPVI / autoclavable.