The QED Sample Pro Bladder Pump is stainless steel and 1.75" in diameter. A 3/4" pump is also available It is fitted with a bladder inside the pump that is timed to be deflated by compressed air that is supplied by the QED compressor. The pressure is released from around the bladder so that water will then be drawn into the bladder. Again the compressed air is used to push against the outside of the bladder(deflating) which forces the water out of the bladder and up the discharge tubing. The pump uses 1/4" OD tubing for both the discharge line and for the compressed air line.(The 3/4" pump uses 1/4"OD and 1/8"OD tubing) The pump can operate down to 200', but requires compressed air from the QED compressor and the QED MP-10 is needed to regulate the water flow.The Sample Pro Pump is easily disassembled, without tools and is simple to clean Additional disposable bladders and accessories are available as well as the air and discharge tubing.