Fender Sealing

Heres the material I picked up today at NAPA.
Its about an 1/8" thick and 1 7/8" wide. Its a sticky rubber dumdum type material.
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Its very sticky but wont soak up water. Now the question is how far up should I put this on the flange. Should I cut the strip down to an inch wide. The flange is about 2" total. SHould some ot this push out the bottom and I smooth it out?
Thanks Rod
That material is for wrapping air conditioning lines. It's a cork based material.