The 6-stem version is the most compatible you're going to get. These will virtually fit all modern keyboards with the exception of the Leopold FC500R (full-size boards) and Leopold FC700R (new Leopold TKL design).
These 6-stem versions WILL fit the Leopold FC200Rs (previous TKL version). They will also fit Filco, Das, CM Storm, PLU, Ducky, and any other major production keyboards.