Common on 1960's and 1970's bicycles, 13/16" posts are becoming difficult to find. They were also a common size for French road bicycles. As always, carefully measure to be sure your bicycle actually uses a 13/16" post as opposed to 7/8". Also, 13/16" is equivalent to 20.7mm and is NOT the same as 20.4mm. 13/16" posts will not fit in frames that use a 20.4mm post. We have provided EXACT measurements of each post in the description.