Which Janome machines does this foot fit?

It is listed for the 4300QDC, DC2019, JNH7700, Memory Craft 11000 Special Edition, Memory Craft 6600P and NPCF50, among other Janome models. Check your machine against the full list before buying.

Can it sew on both sides of a zipper?

Yes. The foot can be set to sew on either side of the zipper, so you can stitch one side and then the other.

How does it keep the zipper straight?

The edge of the foot runs along the zipper teeth and guides it, so the stitching line stays even.

Is it a screw-on or snap-on foot?

It is a screw-on foot. You attach it with the machine's presser foot screw rather than snapping it on.

Do I need a special needle for zippers?

A zipper foot handles the placement, but a zipper needle helps with thick fabric and close stitching. The foot does not include needles.

Is it worth adding if my machine came with a zipper foot?

If your included foot is fixed, this adjustable one adds the ability to switch sides and follow the zipper edge, which helps with lapped and centered zippers.