Theoretical estimation of effective assembly rate of each individual microtubule within a fiber at which the total depletion of GTP-tubulin in the immediate vicinity of fiber microtubule tips may be induced. At crowded conditions (see the text), the total local depletion of GTP-tubulin at the tip of individual, out of fiber, microtubule will occur if microtubule grow at 65 microns/min (Odde ). However, maximal microtubule growing rate is 20 microns/min (Shelden and Wadsworth ). Therefore total depletion of GTP-tubulin cannot be induced in front of individual, out of fiber, microtubule. However, each individual fiber microtubule independently contributes to the depletion. Since their effect on depletion is cumulative, they may induce depletion each growing at rate less than 65 microns/min. In the case of fiber constituted by the four microtubules, depletion can be induced. Indeed, if each of four microtubule grow at ~16.5 microns/min, then in terms of depletion efficiency; 16.5×4 = 66 microns/min, total local depletion may be achieved. At number of fiber microtubules higher than four, depletion will be certainly induced.