Nalgene™ Oak-Ridge centrifuge tubes Type 3119, PP-copolymer PP-copolymer with PP screw cap. PPCO is more resistant to chemicals than PC. Autoclavable. When wet, the translucent test-tube enables observation of the contents. Can be used in refrigerated and unrefrigerated centrifuges at up to 50,000xg rcf. Accessory sealing cap assemblies are available for all sizes.