A bundle of cross-linked actin filaments that is part of an actin-based cell protrusion, in which filaments are oriented such that the plus (barbed) ends are at the tip of the protrusion, capped by a tip complex which stabilizes the filaments. [ http://www.ncbi.nlm.nih.gov/pubmed/12566431 http://www.ncbi.nlm.nih.gov/pubmed/15661519 ]