Alpaca fleece is the fibre that comes from an alpaca. An alpaca is a domesticated species of South American camelid (camels)
Alpaca fiber while similar to wool is warmer and has no lanolin, which some say makes it hypoallergenic. It can be light or heavy in weight, depending on how it is spun. It is a soft, durable, luxurious and silky natural fiber. It has some halo when hand knit and is naturally water repellent and difficult to ignite. Some compare it to cashmere. It has some advantages over wool, in that it is several times warmer. It is reported to be much stronger than wool. Garments made from alpaca are warmer, lighter, softer, silkier and drape more than wool. Some knitters find they get growth in length when garments are knit from 100% alpaca particularly with heavier weights. I have used alpaca in fingering weight quite often and I have not had any issues to report. I'll be working with a worsted weight for a garment in the near future to see what the results are like in that form. I have used many alpaca blends in the past with no negative results. My unofficial results from questioning knitters I know seem to recommend the lighter weights as opposed to the bulky and chunky (4 and under on the Standard Yarn Weight System).
A friend who spins tells me that yarn memory is based on a number of factors that are not all obvious to knitters. She lists the natural crimp of the fibre, the scales on the fibre strand, spinning and plying techniques, yarn weights, the stitch patterns we use as well as the quirks of individual knitter's gauge and tightness or looseness of the knitting.
The following grading information comes from Victory Farm. The first 3 Peruvian names listed below are the ones you are most likely to see on yarn labels.
Alpaca fiber is classed by the micron (u) of the fibers in the fleece. In Canada, Alpaca Fiber is classed into 6 grades, grade 1 being the finest. In Peru, they class by different names: Super Baby, Baby, Superfine, Adult, Coarse. Grading in Peru is done by touch, whereas in Canada, samples are compared to samples which have been tested using a microscope.