Main Page | See live article | Alphabetical index C5 is a standard size for envelopes, a C5 envelope fits an unfolded A5 paper. See ISO 216. an electric moped by Clive Sinclair, see Sinclair C5. This is a disambiguation page; that is, one that just points to other pages that might otherwise have the same name. If you followed a link here, you might want to go back and fix that link to point to the appropriate specific page. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.