A low-PIM, stackable polymeric cable hanger spacer that includes a polymeric base forming a rim that defines a latch surface for capturing locking metal barbs of interface brackets of a metal snap-in cable hanger. The spacer also includes polymeric legs extending from the polymeric base with polymeric barbs for latching to an adjacent snap-in cable hanger or other support member. The base allows the metal barbs to pass through the base when the metal barbs are deflected or compressed toward each other. and then allows the metal barbs to spring back to engage the latch surface and become captured by the polymeric spacer once the metal barbs clear of the rim. The base may have a round toroidal shape with rounded edges allowing the metal snap-in cable hanger to rotate with respect to the spacer.