Type of filler particle used in packable composite:: (A) Fibrous filler particles, (B) Microcrystalline filler particles, (C) Mixture of both, (D) None of the above
Answer is A. Specifically the packable/condensable characteristics are derived from the inclusion of elongated, fibrous filler particles of about 100 µm in length and/or rough-textured surfaces or branched geometries that tend  to interlock and resist flow.
Phillips Dental materials 12th edition pg no 286