The eclipse frenzy is heating up, but before you head outside to stare at the sun on Monday, you might want to take a look at your eclipse glasses first.

There are new concerns about counterfeit glasses that could hurt your eyes. Earlier this week, Amazon issued a recall because the company could not verify if the glasses it sold were safe to use.

Don Ficken, with the St. Louis Eclipse Task Force, recommends looking for two pieces of information printed inside the glasses.

First, the manufacturer. There are only a handful of manufacturers that have been approved to make the glasses:

  • American Paper Optics
  • Baader Planetarium (in Germany)
  • Rainbow Symphony
  • Thousand Oaks Optical
  • TSE 17

Second, look for an ISO number. Most of the numbers end in 2015, the date the standards were set.

Also, when putting on the glasses, make sure you cannot see anything except. It should be completely dark, except for some of the brightest light. And, do not use glasses that have holes or scratches.

“I really prefer to get them directly from the manufacturer,” Ficken said. Anybody can print anything on these glasses. You can’t really stop that, and there’s no way to verify at the end of the day. I prefer the ISO directly from the manufacturer, or someone you know purchased from the manufacturer.”

Tips for choosing safe glasses.