Highly Accessible Vortexer with Easy Functionality

I highly recommend for vortex, which is flexible to use and possesses the option to fit your tubes or use big tubes by removing the top. I use this very often to vortex samples like mixing tissue powder with buffer as with DNA or RNA extraction or other type of experiments. The feature I like the most in this vortex is that the knob shows the rotation speed in rpm units. I have concerns as sometimes the vortex moves faster than the speed indicated on the instrument. So, if it had more speed options, that would be great.