A guide wire assembly includes an inner core wire and an outer tube. The inner core wire has a proximal end, a distal end and a torque transmission portion and the outer tube includes a proximal end and a distal end. The distal end of the outer tube is coaxially mountable over the proximal end of the inner core wire and extendable distally on the inner core wire to the torque transmission portion. The torque transmission portion defines a raised taper which is frictionally engageable by a recessed taper within the distal end of the outer tube to releasably couple the outer tube to the inner core wire for torque transmission therebetween.