These Pyrex® Erlenmeyer flasks with phenolic screw caps are ideal for use as a shaker flask or for mixing, media prep and storage needs. Impact resistant caps with GPI threads are equipped with cemented-in, inert white rubber liners which are resistant to steam sterilization. Their uniform wall thickness provides the proper balance between mechanical strength and thermal shock resistance. For convenience, these flasks are graduated to show approximate capacity and include marking spot. For replacement caps see Cat.No. 1-9999.