Stainless Steel Nickel Plated Brass Stainless Steel (316L) Locknuts Hexagonal locknut to secure fitting Nominal Size (mm)Ext Metric Part Number 16SS-M16 20SS-M20 25SS-M25 32SS-M32 40SS-M40 50SS-M50 63SS-M63 Nicke Plated Brass Hexagonal locknut to secure fitting Nominal Size (mm)Part Number 12B-M12 16B-M16 20B-M20 25B-M25 32B-M32 40B-M40 50B-M50 63B-M63 75B-M75