A two-part sizing system for making colorless, densified fiber pellets of a reinforcing fiber material. The densified product may be advantageously produced by first applying a precursor size composition to reinforcing fiber strands, chopping the reinforcing fiber strands into chopped strand segments, applying a binder size, and densifying the chopped strand segments to form densified fiber pellets. The binder size is formulated using a copolymer of maleic anhydride which generates a product free from discoloration. In the process of making the pellets, the sized chopped strands are densified by tumbling in a rotating chamber for a period of time sufficient to increase their density but insufficient to degrade the fibers to a point where composite articles formed from such pellets have lower tensile or impact strengths than comparable composite articles formed from unpelletized strand segments.