Formerly called Microtubule Cushion Buffer. Contains BST01 in 60% [v/v] glycerol. When diluted in G-PEM to a final concentration of e.g. 5% glycerol, it can be used to promote tubulin polymerization. It is also used to separate microtubules from non-polymerized tubulin by centrifugation and to separate microtubule bound MAPs from non-microtubule-binding proteins.