This is the Part that includes the "Shaft" (STEM) the part that protrudes out the top of the pump and attaches to the bottom of the chair seat.
* Includes bottom parts: HLP-5506H Stem, HLP-5583 Stem O-Ring, HLP-5581 Sel-Loc Spring pin, HLP-5577 Stem Washer, HLP-5509 U-Cup, HLP-5507 Piston, HLP-5579 Stem Piston and HLP-4004H Socket Tube.

* this mostly half of the pump

** Why this part needs to be replaced:
???????????????? Really is the Stem needed to be replace, unless it has been damaged on either end. The other parts (on the lower end of the Stem) do need to be changed out and some times is betther to buy this Stem Assembly if you do not have the tools to properly change-out the U-Cup HLP-5509 as the
HLP-5581 Sel-Loc Spring pin is hard to remove and replace.

* Fits Collins, Jeffco, Veeco, Kaemark and 4 X 4 Belvedere® brand Heavy Duty Hydraulic Pumps
* May fit others but the chair seat manufacure must be a U.S. manufacture

*** Fits ONLY USA made Pumps, 5-1/2" O.D., 4-1/2" O.D. & Belvedere 4 X 4 Hydraulic Pumps

Please allow 1 - 2 weeks to ship