The primary craft for all duties associated with the operation of the SPSS is the Mail Handler Craft

  USPS Issues Primary Craft Determination: Mail Handlers to Perform Duties Associated with SPSS Operation

"...On June 2, 2015, the Union recieved the Postal Service's determination of craft jurisdiction for employees operating the Small Parcel Sorter System (SPSS), which is currently deployed in five pilot test locations, and will be deployed shortly in twenty-six other facilities around the country. As set forth in the captioned letter, the Postal Service has determined that "the primary craft for all duties associated with the operation of the SPSS is the Mail Handler Craft." Follow this link to read the NPMHU notification to Local Presidents and USPS jurisdictional craft determination letter. (pdf) ..."

Reference: www.npmhu.org