Solid construction with plenty of metal parts normally found in plastic on other pumps.  The one thing I like the most is that the Air Tower HP eliminated the locking device which causes stress on the valve stem and premature wear which leads to failed stems.  Without this device the pump depends on an O-Ring to prevent the pump from losing preasure and adhear to the stem.  The question is "How long will the O-Ring do the job correctly.  They do provide you with 2 spare O-Rings located in the handle of the pumpm but as a precaution I ordered a Rebuilding Kit, just to have on hand as I suspect this pump will last me many years.