free motion quilting foot
 

I have a Viking Sapphire 835. I recently bought a free motion foot, but I think I bought the wrong thing. This is what I bought.... http://www.amazon.com/Genuine-Husqva...+quilting+foot , but I'm wondering if I should have bought this.... http://www.amazon.com/Viking-Open-Fr...+quilting+foot. Can someone clarify this for me please? Thank you!

They both do the same thing. Most times people prefer one type over another for visibility reasons. They will both get the job done.

If it were me, I'd go with the clear plastic one -- easier to see both where you're going & where you've been.
I personally have a clear plastic open-toed foot for my machine -- best of both worlds -- but since you already have one foot, why not try it out & see how you like it. Can you do that without destroying the packaging?

What is the purpose of the spring?

The spring makes the foot hop which is not necessary for FMQ, both will work as one said it is a personal preference. The first foot is really good for echo quilting as shown in picture

I also have a Viking Sapphire and the Viking free motion foot I use is neither of those pictured...it is clear and has an open rectangle. It attaches on the regular arm just like your A and B feet. I did order the one you have as well for echo quilting (the guides are to keep you uniformly at a distance from the previous outline quilting) and have not used it as that was a recent purchase. My regular FM foot works well, but I think the one you ordered will do fine too.

It's a matter of preference and the type of quilting you like to do. The second one is a 'hopping foot' or spring foot that hops up and down as you stitch. It holds the fabric down when the stitch is made, then releases the fabric a bit. There's a special setting on your machine for this foot to work. It's good for tight stippling. The other foot is good for larger stippling and echoing. I know people who hate the hopping foot as they find it distracting. Also, check to make sure the the one on amazon is a real Viking brand foot. With a foot with moving parts, I would get the genuine Viking brand, not a generic.

why not check Viking's web site out. I do know there are different FMQ feet, open toed, closed, clear. So it could be the right foot but just a different kind. I'd go to Vikings website and find the manual on accessories and see what the numbers are. All of my viking feet have a number engraved on them. Its probably easier to google your machine name and include either accessories or manual in the search. When you see Vikings website click on that one and it'll take you to your machine. Some of thier machines are archived so you don't see them as easily as other but they are there.

Here you go, looked it up for you

This is for your machine;
http://new.husqvarnaviking.com/en-US...s/SAPPHIRE-835
This is for the extras, you might have to click on show more at bottom of page to see all the extra feet.
http://new.husqvarnaviking.com/accessories#1212

the spring helps keep your thread from breaking when you move the quilt. it's a split second of stability on the fabric as you stitch. and it does help.

The second one would be my preference. Mine hops and has a spring, don't know why but it all works.