Medical devices and methods for making and using medical devices are disclosed. An example medical device may include a guide extension catheter. The guide extension catheter may include a proximal member having a proximal outer diameter. A distal sheath member may be attached to the proximal member. The distal sheath member may have a distal outer diameter greater than the proximal outer diameter. The distal sheath member may have a proximal end, a distal end, and a longitudinal slit extending at least partially between the proximal end and the distal end. An expandable member may be attached to the distal sheath member and may extend along the longitudinal slit. The expandable member may be configured to shift between a first configuration and an expanded configuration.
