The pull-out hose puts less stress on the valve.
Blackburn's Presta-only thread-on head sits on a short pull out hose to give more options on which position you pump from. Nervous about unthreading that valve when removing the pump? Enter one of the Core Slim's awesome features: the Presta Valve Tool. Simply unthread the tool from the back of the pump and tighten your valve prior to threading the hose on. With a narrower and slightly longer body than the Core pump, the Core Slim is a great choice for inflating higher pressure 700c tires.