Small Prototyping Machinist here, ordered these 5 ER16s because i needed to be able to set more tooling up without having the remove and replace tooling for different jobs. These came packaged in the twist and lock containers made for CAT40 holders and were enveloped in a thick plastic with oil to keep them from rusting, very content with the quality of the holders themselves, fit my ER16 collets without issue and ran all five of them up to 4000 RPM (machine max) without any issue. Will be ordering more in the future.