. . . what you use to stay fit. Well I walk to work – even in the frigid weather lately – but for less stress exercise – this punching bag is tops! (click on thumbnail to see larger image) Bought as a Christmas present for my son, all human family members give it a solid whack when passing by in the hall. The plastic base, about 18 inched in diameter is filled with water, the bag on top is filled with air, and the metal rod attaching the two is height adjustable. When smacked, the bag promptly bounces back on its spring. The drawing is General’s woodless graphite 8B – on very soft unknown brand of paper.