Handlebar shims have always been part of the Hubjub toolkit for assembling the bike from your collection of components.
These are for solving various problems including accommodating traditional bars in oversize clamps.

22.2 - 25.4mm: ridged aluminium anodised silver.
25.4 - 31.8mm: aluminium and anodised black.
26.0 - 31.8mm: aluminium and anodised black.