WN flanges is the most popular type of flanges.ASTM A182 F304 is a American standard grade of stainless steel.The other popular grade is A182 F316.ASME B16.5 forged flanges inculding WN flange,SO flange,SW flange,THD flange,LAPJ flange,BL flange.All types of flanges have pressures:150#,300#,600#,900#,1500#,2500#.