I'm updating this thread in case there are any lurkers or for future reference. Anyway, it's not just the followers that changed on the new G31 mags. They partially redesigned the magazine body and added two ribs to the inside, one on each side that go from the feed lips down around 1.5 inches. Essentially the area where the magazine is tapered. I'm assuming this is keeping the bottle necked cartridges in better alignment as they go from a staggered row to a single row at the feed lips. The new follower has slots on either side to account for the ribs in the mag body. I test fired yesterday, and the new design works great with 357 Sig Gold Dot 54234. The spring pressure is much stronger, and there's no nosediving of the bullet as it's raised to the feed lips. The #5 followers alone are not an improvement, as I tried them in my older G31 magazines. It's surprising Glock made the redesign this late in the game. 357 Sig isn't a popular caliber, so they could have left it alone. I'm thankful they did, since now I have more faith in my 15rd mags. The part number on the back of the mags is 4363-05, and the box is MF31015.