Equal-i-zer and Fastway E2 are both brands sold by Progress Mfg.
Progress MFG. Inc.
They look very similar, as you can see from the video somebody else posted..
The Equal-i-zer branded product has 4-point sway control and is made in the USA.
The Fastway E2 product has two points of sway control and is made in China.
You'll note that nowhere in the product web sites is the Equal-i-zer product referred to as E4 nor is the Fastway E2 product referred to as Equal-i-zer... but dealerships often do. Either they don't know any better or perhaps some internal part# includes those incorrect terms.