Both blended winglets and split scimitar winglets can be retrofitted onto older aircraft models. For example, it is common to see early Boeing 737 models such as the 737-800 and the 737-900ER ...

They represent a step up over blended winglets, thanks to "new strengthened spars, aerodynamic scimitar tips, and a large ventral strake." 52 Boeing 737-800s will be retrofitted with the scimitar ...