Skew can be especially prominent in cables which use different dielectrics on different pairs, the so-called "3X1" or "2X2" constructions. These are most common in plenum-rated premise cables where TeflonTM and polyethylene are used on adjacent pairs. Skew can be minimized by putting the "faster" compound on the tightest lay-length (slowest pair) and by modifying the chemistry of the dielectric to reduce the Dielectric Constant (and therefore Velocity of Propagation). All other things being equal, the 4X0 (all Teflon) will have less skew.