A quasi monofilament having a high strength polyethylene fiber core with an adherent, abrasion resistant polymer sheath is prepared by feeding the core yarn through a crosshead die, while simultaneously supplying a polymer melt at a temperature greater than the melting point of the core yarn to the die, for sheathing the core yarn within the die with the melt under a sufficient pressure to cause the melt to adhere to the core yam. The abrasion resistant polymer sheath includes an effective amount of a first polymer having ethylene crystallinity, a density of at least about 0.94 g/cm.sup.3, and a melt index of less than about 0.1 g/10 min. The composition used to sheathe the core yarn is characterized by a weight average tensile strength at yield of greater than about 13.8 MPa. The quasi monofilament has utility in applications subjected to high abrasion, such as sports fishing lines, kite lines, dental floss, "weedeater" lines and tennis racket strings.