Personally, I have not used their services, but I will gladly share what I know. If you look at RockAuto reviews, many praise them for a huge selection of auto parts at really nice prices, this is a big plus for those who repair their car themselves or just want to save money. Delivery, they say, comes quickly and without surprises, which is also pleasing. But there is a downside: in the same RockAuto reviews, they sometimes mention difficulties with returns if something does not fit, or the lack of live support, only correspondence, which is not convenient for everyone.