November 25, 2019 2 min read

This story originally appeared on PCMag

Tesla’s launch of the Cybertruck last week divided opinion, mainly because of the way it looks. However, what everyone was left talking about is how the ultra-strong windows didn’t survive having a metal ball thrown at them. Elon Musk has now explained why.

As The Verge reports, Musk looked as surprised as everyone else when a heavy metal ball was thrown at the Cybertruck window and it smashed.

Franz throws steel ball at Cybertruck window right before launch. Guess we have some improvements to make before production haha. pic.twitter.com/eB0o4tlPoz

— Elon Musk (@elonmusk) November 23, 2019

As the video included in the tweet above demonstrates, pre-launch testing saw the same metal ball bounce off the window, so what went wrong at the launch?

Related: Tesla Unveils its Cybertruck, With a Price Starting at $39,900

Elon Musk revealed in a tweet what happened. It wasn’t that the windows couldn’t handle the impact, it turns out the previous sledgehammer hit to the door (to prove its durability) had cracked the base of the glass panel. This couldn’t be seen externally, so the windows looked undamaged, but they’d actually lost their strength before the ball was thrown.

The positive to take away from this is that even if one of the windows suffers a crack, a heavy object hitting them won’t pass through the glass. The windows retain enough strength to stop the projectile from entering the cabin and injuring the occupants. I’m also sure Tesla will now be working to improve the door design so as to stop any impacts from cracking the lower section of the glass.