This package includes (8) HDG (Hot Dipped Galvanized) Square U-bolts, (16) HDG Flat Washers, (16) HDG Lock Washers, and (16) HDG Heavy Duty Nuts (use a 7/8" wrench/ socket). The 3-1/16" width is the clear Inside measurement between the "Legs" of the U-Bolt and will fit on 3" x 3" axles or cross members. The 4- 5/16" Height (Length) is the inside dimension measurement from the top inside of the "U", to the bottom tip of the "Leg". ATTENTION: To determine the Height (length) of the U-bolts that You need, measure the total height of the metal and members to be "clamped" and add 13/16" for the nut and washers, That will be the Inside Height that You Need. CUSTOMER'S QUESTION: Can stainless steel nuts be used on these hot dipped galvanized u-bolts? ANSWER: No, only Hot Dipped Galvanized nuts can be used on HDG U-bolts because the Hot Dipped Galvanized protective Zinc layer adds more thickness to the 1/2"-13 U-bolt threads. HDG nuts are threaded larger to accommodate for the added Galvanizing. Look at our other listings for multiple quantities in order to save on shipping. Note: Hot Dipped Galvanized means that the U-Bolts and hardware, are dipped into a tank of 830 Degree F molten zinc. VYT-Tmw