Z366-250-B57 by Hermle is a 14-position insert for 5 ml and 7 ml tubes in the Z366-250 swing-out bucket, sold in a pack of 2. Enables 5/7 ml tube centrifugation at up to 4,500 rpm (3,780 xg) in the Z366-250 bucket system on the Hermle Z366 and Z366-K universal centrifuges.