NASA's standards for eclipse-viewing safety:
1) Have certification information with a designated ISO 12312-2 international standard
2) Have the manufacturer's name and address printed somewhere on the product
3) Not to be used if they are older than three years, or have scratched or wrinkled lenses
4) Do not use homemade filters or be substituted with ordinary sunglasses - not even very dark ones - because they are not safe for looking directly at the sun
Just be mindful of what's being purchased and be sure the above standards are all met ... "frying out your eyeballs" doesn't sound like much fun.