Myler Stainless Steel 3 3/4" Dee without Hooks, MB 06 Mullen with Low Ported Barrel, Level 2-3 _3" Dee on Pony Sizes_ The MB 06 is a Myler alternative to the traditional mullen, but it has a wide low port that allows the tongue to pass under it comfortably. The port is ¾" high, just enough to allow the horse’s tongue to elevate slightly and swallow but not high enough for palate pressure. When the reins are engaged, the 06 applies pressure primarily to the bars and lips.