29 ELEMENT sprag, i use the borg dual cage but others will be suitable too, Now if the unit came with the later GM sprag with the 15 percent wider roller pieces I will try to replace with one of those if available, Bear in mind while you can put the borg sprag in place of one of those and be fine , You should not, cannot put one of the late wider Gm sprag in place of the older unless new ring gear and center used.