 35 anti-aircraft cannons in single mounts or four in two double mounts, and depth charge racks.Thirty-six vessels were completed from late 1941 to the Autumn of 1943, in two series of 18 boats each.The first series included hull numbers from "MS 11" to "MS 16", "11"–"16", "21"–"26", and "31"–"36"; the second "MS 51" to "MS 56", "61"–"66", and "71"–"76".