There are few hard limits there. Researchers are finding that you can do a lot of different, clever things with the material. If you’re looking at a powder process, fiber length needs to be less than the diameter of the powder you’re working with.

If you’re working with a filament or pellet, then you can use a larger size pellet width and go longer in terms of fiber length. Pellets will still have a limitation if you’re going to pre-compound and put those fibers in the pellets.

With a filament, however, you can use a range of fiber lengths, including fairly short because you have that continuous length of filament that you’re able to put fibers in. For example, there are carbon-filled nylon filaments with between 30 and 40% of fill by weight and fiber lengths on the order of about 200 microns.