For Hardwired Power Strips, what is the difference between models that end with “1” and without “1”?

With or without ears (mounting tabs on both ends)
Please compare product pictures of the same size and color, please pay attention to the lower left hand corner, models’ SKU # end with “1”, it has ears; without “1”, without ears.
Mounting for without ears type is done by Clips, which you can see by clicking on the “Clip” word hyperlinks at the end of Installation Guide on each hardwired power strip product page.

What about the “Old” and “New” model or style?
Model SKU # has “Y” or “Z” are old style. The new style is about 1.25″ in height, whereas the old is about 1.55″, 1/4″ taller. Please click on “Specifications” tab on all product page to see the “Measurement” if it fits your need. Old models will be phased out gradually.