Dear Lifehacker, I just wanted to know why with Blu-ray discs, some of the are softer than the others. As in, when you slightly bend them they are more flexible. Some discs even feel flexible when you hold them in your hand. Does this mean that some Blu-ray discs are higher quality than others? Thanks, Jack
All Blu-ray discs are effectively identical in physical dimensions, because the margin of error that a Blu-ray discs player’s laser can read data from is really small — if one disc was noticeably thicker than another, it wouldn’t work.
The difference in some Blu-ray discs being harder to bend than others mainly comes down to one thing: the protective coating. Unlike DVDs, a protective anti-scratch coating is mandatory on Blu-rays: it’s part of the design standard.
The formula for that coating isn’t a mandated thing though, so each Blu-ray disc manufacturer has its own. Some are sturdier than others, and this contributes to the difference you might feel when testing a disc to see how bendy it is.
Similarly, the polymer chemistry mix used to create the discs themselves varies from manufacturer to manufacturer, just like the coating: some manufacturers use a plastic that’s cheaper but isn’t quite as strong.
One last thing: if you compare a Blu-ray to a DVD or CD, you’ll find that structurally it’s far superior. As well as being a bit thicker and having that extra protective coating, the inside of the disc — the centre circle that doesn’t have any data on it — is much better designed and less likely to crack, which reduces the risk of a Blu-ray disc shattering when it’s spinning at 5000rpm inside your player.
This story originally appeared on Gizmodo.