You’re probably already preparing for the August 21 solar eclipse, right? It’s going to be spectacular, especially for those in the path of totality, which stretches across the U.S. from South Carolina to Oregon. No matter where you live, though, if you want to watch the eclipse, you should get ahold of some eclipse glasses. To make sure your glasses are up to safety standards, your specs need to follow a few guidelines from NASA before you look up.

First, you should be able to see the manufacturer’s name and address somewhere on the glasses. There are five brands of eclipse glasses that the American Astronomical Society has verified as meeting eclipse safety standards:

  • American Paper Optics
  • Baader Planetarium (only the AstroSolar Silver/Gold film)
  • Rainbow Symphony
  • Thousand Oaks Optical
  • TSE 17

You should also verify that the glasses list the correct certification information, confirming that they’re safe to use when looking directly at the sun. Somewhere on the glasses it should say that the glasses meet the ISO 12312-2 transmission requirements, and you’ll see an ISO logo from the International Organization for Standardization.

This is what your glasses should look like, according to NASA’s guidelines [PDF]:

NASA [PDF]

Even if your glasses have all the right information written on them, make sure to take a second look. Be careful not to use lenses that are wrinkled or those that have scratches on them. They should also be relatively new—don’t use any that are more than three years old.

We previously wrote about Warby Parker's free eclipse glasses, which you can pick up in the company's stores in August. We've reached out to the company about whether their glasses meet these guidelines and will update the story when we hear back.

Read the rest of NASA's eclipse safety recommendations here.

Update: Warby Parker has confirmed that their free eclipse glasses are made by American Paper Optics, a certified brand. View away!