A handy, little, space saver, this circular twelve place polypropylene test tube stand has four 25 mm dia holes & eight 19 mm dia holes in its top plate. The base has matching hemispherical wells & 16 vetical pins for drying tubes surrounded by a trough to catch drippings. This autoclavable rack can be easily disassembled for cleaning purpose. 19 mm & 25 mm ? Tubes