Why do goggle lenses have "posts?" I recently acquired a set of MTB goggles. Both the lens it came with and an alternate lens I purchased claim to have "posts," which I understand to be two small hourglass shapes protruding outward from the lens, one on each side of my face. If I have the nomenclature wrong, please tell me. The image below (borrowed from this answer) shows "posts" on it, too, although that's not the brand I have. Knowing that it's a feature on competing models makes me all the more certain it has a significant purpose. ![Goggle picture]( What are they for? Changing out the lens? Protection? Something else?

Some environments are much dirtier than others, and goggles are continually getting soiled. Sometimes a large amount suddenly gets deposited, effectively blinding the rider.

One solution is to have a thin plastic sheet attached across the goggles. _It_ gets dirty, but not the goggle lens itself, and it can be pulled off and replaced.

Even better, to avoid the time required to apply another cover, a stack of them can be installed, and only the dirty top layer is removed each time.

> Tear-offs are thin plastic sheets that are installed onto the goggles and torn off when they get too dirty to see through. They protect goggles from scratching and ensure a safer and uninterrupted riding experience. They’re attached to pegs on goggles with only the top tear-off’s tab hanging out on the left for easy reach and tearing.
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> — What are Goggle Tear-Offs and How to Install Them - Risk Racing