Its the "arch" shape thing in the wiper, like 4 (or less) "bow" holding the wiper blade/rubber. Those are the one that lost its strength after long term usage.
Try pull up / stick up ur wiper, comparing its condition when its new VS when its "old, you will able to see that after long time, those arch doesn't hold the blade as strong as they use to do.
But frankly, when accs ppl point out to me that my wiper "bengkok" abit, i also cant differentiate it.
My most regreted thing about wiper is not having change them when they start to have a little bit split end in the tip of the wiper blade, ends up with pernanent wiper scratches :cry_smile:
I use to thought (too lan si already) that since i have taken good care of my rubber wipers (last > 2 yrs) it shld still able to do d job although a little split end occurs, but fren, learn from my painful lesson, replace it!!