Our most economical model. If you only need an air pump to occasionally inflate your exercise ball or other small inflatables, this will do the job, but larger models are recommended for frequent users or for larger inflatables. User notes: This hand-held, small-sized air pump is easy to carry and store. With the small shaft size, it does take a lot of up and down strokes to fill a 65cm exercise ball. Our test required over 350 up and down strokes to fill the ball. If you pump at a steady pace with no breaks, it should about 4 minutes to fill a ball.