An all purpose zipper is the most commonly available and commonly used zipper. An all purpose zipper is a fairly lightweight zipper with small teeth. The end of the zipper has a lock which holds the zipper tape together, preventing the ends from coming apart.
It is the type of zipper you will use as a closure in most garments. Dresses, skirts, slacks and blouses are the type of weight that use an all purpose zipper. An all purpose zipper tends to bend with a garment verses a heavier type of zipper that would cause a seam to not bend or flow with the line of the garment.
New all purpose zippers are available in lengths from 4" to 24" at 2" intervals. They are available with polyester teeth or with metal teeth that match the color of the zipper tape the teeth are attached to.
To replace a zipper, when the exact length of zipper is not available, chose the next longest zipper to the zipper that is being replaced and shorten the zipper to the length you need.