Bought a few of these last year, and had one that was DOA. Was told to ship it back for warranty. It cost me nearly four dollars to send back a $5.50 servo, but I was frustrated that I had one out of four that didn't work. When they DO perform, they work fairly well for a cheap servo on foamies.
So, I just received an order that included eight more of these servos. When preparing them for installation, two of the eight were DEAD out of the box. Save yourself some frustration, and spend a few more dollars for a better quality servo. You won't regret it.