if you mean the R1 1x1, R2 1x1 etc. that is what keycap you want. the keycaps in the different rows on your keyboard have slighlty different shapes. also the modifiers are bigger etc.
if you want a full custom keycap set (all keys), then you can go to the custom keyboard designer and after you press add to cart you can choose if you want it as full keyboard or only the caps, so you don't have to fight with the different key cap types.