This package includes (4) Stainless Steel U-bolts and (8) Stainless Steel Flat Washers and (8) Stainless Steel Lock nuts. These U-Bolts are made in the USA out of high quality 304 Stainless Steel, and they along with the 304 stainless hardware included, hold up well in wet/salt water environments. The 3-1/16" width is the clear Inside measurement between the "Legs" of the U-Bolt. 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 of the U-bolts You need, measure the total height of the metal and members to be "clamped" and add 13/16" for the nut and washers. To prevent "galling" (also known as "thread lock") use a hand ratchet or wrench to run up and tighten the nuts, do not use a an impact or powered socket driver. If a U-bolt is accidentally dropped in sand, thoroughly clean off the wax coating and re-apply lithium grease or candle wax to the threads to prevent galling. These U-Bolts will fit on 3" x 3" cross members, such as 3" x 3" box steel. Magnetism - In its originally formed state, 304 stainless steel is Austenitic and not attracted to a magnet but when threads are machined into the U-bolt 304 blank or when a washer is punched out of a 304 sheet blank, the working of the metal causes it to become slightly magnetic and a strong Neodymium magnet will pick them up, but a plain magnet will barely lift them, but they are still corrosion proof. CPA-4pk .