Other than the price in the kits what makes them different??
Razzi front lip and extreme dimensions front lip??????????????
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EXTREME DIMENSIONS
RAZZI
are they good kits?? they look clean and a little agressive especially in black, thats kinda the look im going for
Extreme dimensions is a knock off company. Razzi is the real company. Notice how the cars used are exactly the same?
Honestly, I'd go with Razzi. I don't trust anything that has a blue background and is watermarked to hell.

Your fight begins tonight.
not my taste but they are made pretty good if u go straight through razzi, not too hard to install either, just gotta chop the front up a little
Razzi produces ABS material type lips, so they are more identical to the material used in your oem bumper. I don't know about the cavi, but the Fire lip from Razzi is actually a "cover" that you place over your existing bumper, which I find no problem with and can be molded to look stock. Anyways, it seems ED uses what they call a "composite" material. Which could be the same as the Razzi kit or a fiberglass-hybrid. Either way it is a knock-off. Erebuni also supplies knock-off Razzi kits, and from what I understand they are going under and are offering their kits at $179 a pop, if they are still available.
I would say go with the Razzi kit, might be slightly more expensive, but at least it is made by the original designers.
The name brand is generally what sets the prices apart, also the quality of material of the lips.