They have recently dropped the SP from the stamp. The "Zero Sinus" is the SP. No difference at all. I just got one in along with 2 APs. Got to throw them a bit. Love them all. I think the "SP" will make the bag right away bc of the grip and feel. But the APs may well be the driving putter while the "SP" handles appraoch and wind putt duties.
Bolt / Halo / Trespass / Villain / Giant / Flow / Striker / Escape / Trident / XxX / Core / Fuse / Mace / Sinus / Mercy / Pure