This product is a hot dipped galvanized boat trailer equalizer bar. It is commonly called the EQ-356. It measures 6 1/4 inches from center to center on the two bottom holes and measures 2 1/2" inches tall. This equalizer bar, or pivot bar ties together the suspension on tandem axle trailers. It has 9/16 inch diameter nylon bushings. It measures 1 3/4 inches wide. This equalizer bar is more common on boat trailers than on utility trailers, but has seen a variety of uses. It's galvanized finish will help keep rust from forming.
The 9/16 Inner Diameter bushing that comes pre-installed is suitable for most land trailers. If the purpose of this equalizer bar is for a boat trailer, you will most likely need to replace that bushing with a bushing with a 1/2 inch inner diameter, as it is more common to have 1/2 inch diameter spring bolts on boat trailers. The appropriate one for this Equalizer bar measures 11/16 Outer Diameter, available here Trailer Leaf Spring Bushing 1/2 inch ID, 11/16 inch OD