This adapter is required if you want to install Shimano 24mm HollowTech II cranks on a PressFit 30 frame with a SRAM Press Fit30 bearing assembly. In case you are wondering, a BB30 spec frame has a 42 inner diameter BB shell and a Pressfit 30 frame has a 46mm inner diameter BB shell. Made from lightweight Delrin. Does not include the PressFit30 bearing assembly so order that too if you don't already have one.
Works on Pressfit30 frames only with a SRAM PressFit30 bearing assembly - (i.e does not work on BB30 frames)