All new 737s use split-tip winglets, which are more efficient than the simpler blended winglets previously used.
However, for no clear reason, they use two different types of split-tip winglet:
- New 737 Next Generations (the 737-700/-800/-900)1 use split-scimitar winglets, which have a main body shaped like a blended winglet, but with its upper tip hooked backwards, and also have an additional scimitar-shaped fin projecting outwards and backwards from the upbend in the winglet.
(Image by Mnts at Wikimedia Commons.)
- The 737 MAX series uses the eponymous MAX winglets, which have a simpler shape than the split-scimitar winglet, looking essentially like if someone decided to put a winglet on the bottom of the wingtip in addition to the one at the top.
I don’t get it - why go to the trouble of producing two slightly different styles of winglet alongside each other for two mostly-similar families of the same aircraft? Why not just go with the more efficient style of the two (be it the split-scimitar winglet or the MAX winglet), and use that on both the Next Generation and the MAX?
1: The 737-600 also belongs to the Next Generation family, but it left production long before the Next Generations switched from the blended to the split-scimitar winglet.