You can actually see a piece of pipe insulation at mine, upper left corner
I tried to paint them black. It looked great until the first rain storm.
Take the small diameter ones, the big ones are easily too big.
Some come with an adhesive strip, that might help you to keep them attached.
I had no strips on mine and lost one (but I had a stack of them).
I run my lower grill block all year, no problem (though it has been close to overheating once last year when stuck in a traffic jam during a record heat spell)
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gmeter or 0.13 Mmile.
For confirmation go to people just like you.
For education go to people unlike yourself.