This is an EZ Loader Brand Equalizer Bar for Boat Trailers using what is referred to as Reverse Curve, or Open Eye Leaf Springs. This Equalizer Bar is easily identified by the (3) Bolts used to Mount your Assembly. You will most likely be using a 5/8" x 4" Bolt Mounting through the center Hole, and either 1/2" or 9/16" x 3 1/2" Leaf Spring Bolts through the two outer holes. This is a very common and standard equalizer bar on Ez Loader Brand trailers. From Center Hole to Center hole on the two outer holes measures 7". You would have this product on a Tandem Axle trailer only with two axles, and four leaf springs.