The SoftFlask Speed 500ml is designed for running vest and pack pockets. Its pinch-welded construction gives it a slim, tapered profile that helps it slide into place.
HydraPak's fit guidance gives the filled flask dimensions as approximately 210 × 80 × 55mm, with suggested pockets around 210–230mm long, 75–100mm wide and 55–60mm deep. Pocket shape and retention should still be considered when checking individual vest or pack compatibility.
Remove excess air before running if you want to minimise fluid movement as the flask compresses.