Angle is more important than diameter: (n,n) Single-walled carbon nanotubes (SWCNTs; see picture) are less reactive than fullerene towards exohedral addition reactions. The reactivity of (n,n) SWCNTs towards sidewall addition reactions depends on the pyramidalization angles of the tube C atoms. Even with the same diameter, SWCNT has a much smaller pyramidalization angle because of the cyclic bending (instead of spherical as in fullerene). The difference between inside and outside reactivity of SWCNTs is only moderate for typical examples such as (10,10) SWCNTs, and the accompanying endohedral adduct formation seems possible.