Abstract: A bicycle frame for employment in a bicycle for riding by a user in a substantially vertical as-used position. The frame has a shape which defines an aperture within the interior surface of a surrounding frame. The frame is preferably formed of planar material which has ends which do not block the view into the aperture when the bicycle is ridden. Whereby space for indicia on an inserted vertically disposed planar member is maximized. The planar member has a perimeter defining a shape that is complimentary to the shape of the aperture and when engaged therein provides support to the frame to prevent deformation thereof when in the as-used position under a load. The indicia positioned on the planar member may be advertising which can easily be changed using removable planar members with different indicia.