The purpose of this standard is to establish selective lists of steel square measurements for motorized and towed material. 1 0 o mm 1st Series (1) 2nd Series 6 8_______ ________JK> _________12 _________________ _____________________________1^3 _ _________14________ _________16_________ 20 _________25______________ ________28_________ ___________________ 30 _ ________32^ ________ ____________________35___ ________40____________________ 50 (1) The measurements of the first series must be caught with preference.