SOLD - This previously-owned/used Barnstead Maxi Mix I test tube mixer, model: M16715, has a vortex mixing speed of 300 rpm. With a 4-inch top diameter, it can simultaneously mix a total of four (4) or more test tubes.Condition: Tested, fully operational, clean. Sold as is without warranty expressed or implied. Buyer is responsible for determining the suitability of this product for their application.