Amazon is refunding customer purchases for protective solar eclipse glasses that it hasn’t been able to confirm come from a reputable manufacturer, according to a safety notification from the company.

Excitement has been building for the upcoming solar eclipse across the United States on August 21st, and would-be eclipse viewers have purchased protective glasses from retailers such as Amazon.com. However, not all of the glasses found on the site are safe to use, with some vendors selling counterfeit or unsafe versions.

Amazon appears to have been cracking down on these suspect glasses. Pages for products such as “MASCOTKING Solar Eclipse Glasses 2017 - CE and ISO Certified Safe Shades for Direct Sun Viewing -- Eye Protection” and others that the company hasn’t been able to verify as coming from a recommended manufacturer have been removed from the site. Customers who purchased these glasses are getting refunds, along with a warning not to use them. The notification also says that customers don’t need to return the glasses in order to get a refund.

In a statement to Oregon broadcaster KGW, Amazon said that it made the decision “out of “an abundance of caution.”

Safety is among our highest priorities. Out of an abundance of caution, we have proactively reached out to customers and provided refunds for eclipse glasses that may not comply with industry standards. We want customers to buy with confidence anytime they make a purchase on Amazon.com and eclipse glasses sold on Amazon.com are required to comply with the relevant ISO standard

Amazon also indicated to KGW that customers who purchased glasses but did not receive a notification e-mail purchased ones that were safe to use. The retailer did not disclose how many glasses have been recalled. KGW also reports that some retailers have been caught off guard, saying that their products have been certified, but that Amazon pulled their products anyway.

Having the right glasses is of particular concern, especially as demand for them soars in the days leading up to the event. Staring directly into the sun is can damage your eyes, and would-be eclipse viewers could be purchases and using products that won’t properly protect them. The International Organization for Standardization has set forth guidelines for glasses, which block out all but 1/100,000th of the Sun’s light, and only a select group of manufacturers have produced glasses that are recognized and approved by NASA and the American Astronomical Society.

Update August 13th, 20177, 2:30PM: MASCOTKING replied to our query via Amazon, saying that they are “are submitting to NASA and Amazon,” and that anyone who is dissatisfied will get a refund.

Update August 13th, 20177, 4:30PM: Included statement from Amazon issued to KGW.