The DOS is a handy piece of equipment but I'd have to say that the pump heads are poorly made. The orange plastic "wall" that the roller pushes the pump tube against is thin and not supported well due to the design they use to make the cap removable by "pinching". The wall breaks frequently due to the rollers pushing against it and I have to buy the replacement pump head caps more often than should be necessary. We shouldn't need to purchase these parts several times in one year. Also, it makes a horrendous creaking sound constantly when the pump heads operate because it is pushing on the plastic.