In general, it is more risky to purchase generic PC RAM.
Choose a reputable seller who tests and guarantees compatibility with your model Macintosh, offers a lifetime warranty, and a no-cost return if it doesn't work. On MR. members have often recommended Crucial, and if you are in the USA, OWC (MacSales) and Data Memory Systems.
Just remember that companies "game" dealram and RAMseeker by offering substandard RAM at a low price, then try to switch you up to their more expensive RAM. Here's an example from the low price leader today:
"$72.99 Generic - is available for the the price displayed on this page and is intended for the budget minded customer that is not doing mission critical work and is not trying to get the best performance or reliability from their machine. 1 year limited warranty"
1 year warranty and not for mission critical work and not for someone looking for reliability or performance. Yeah, gimme some of that then. None of the work I do is important, and I WANT a lower performance machine that is less reliable.
Gee... for only $30 more I can get the more reliable RAM with a lifetime warranty.