A materials kit for 3D printing can include a powder bed material including from about 60 wt % to 100 wt % composite fibers having an average aspect ratio from about 3:1 to about 30:1 and a fusing agent including an energy absorber to absorb electromagnetic radiation to produce heat. The composite fibers can include glass fibers coated with an encapsulating polymer, wherein the glass fibers can be included at from about 5 wt % to about 40 wt % based on the total weight of the powder bed material.