Abstract: Drill string stabilizing sleeves (20, 24) are provided for use on a drill string (10) to guide the drill string during drilling. The stabilizer sleeves are replacable and may be manufactured at relatively low cost. Each sleeve includes a cylindrical body (28) having a number of well bore contacting surfaces (34) formed on the outer surface thereof. The surfaces are separated by grooves (38) to permit flow past the stabilizer sleeve. Slots (40, 42) are formed through the cylindrical body on diametrically opposed sides. The slots pass through the well bore contacting surfaces to the inner surface of the body. Flats (44, 46) are provided in opposed sides of the drill string section where the stabilizing is to be performed. Cylindrical segments (54, 56) are positioned within the flats and continue the arc of curvature of the drill string section. Each of the cylindrical segments, in turn, includes a flat (66, 68) for accepting locking blocks (78, 80) inserted through the slots in the cylindrical body (28).