I thought it came with these
Crutchfield Customer Review (What's this?)
I would consider them more of a deterrent than theft prevention. Since the 450R feet are attached with rubber straps theft could occur from just cutting the straps. That of course would ruin the feet but these days you never know. Still with as expensive as the system is, I considered that something was better than nothing. I got them after installing and realizing that the feet didn't come with the locks included as I thought they had.
Pros: Installs easily
Cons: Should be included with the feet for the price. Not much of prevention, more of a deterrent.