Response to Hello, the SPX1600Z2 is for Northstar pumps prior to 2003, while SPX4000SA2 is for pumps 2003 and later. 

An image is worth 1,000 words! Add an image or two to your comment to help ensure it is understood accurately.

Yes, please email me exclusive discounts, swimming pool tips and helpful how to guides. This comment may be posted on a public site. Do not include: HTML, references to other retailers, pricing, personal information, or any profane, inflammatory language.