I run an old Cateye Vectra comp on mine...It's old and matches the old bike well. It also was included with the $10 I spent on the bike. Currently it resides on the handlebars but it was previously mounted on the very back of the top tube or alternately on the seatpost and had the sensor on the rear wheel. It doesn't look pretty but I have a set amount of miles that I want to get each day with the intent of increasing my mileage and speed. Having to get off your bike and look under your seatbag isn't fun so it now is on the handlebars, where I can see my mileage. Of course this is a 25 year old Raleigh conversion. When I get my Cinelli (when I can save the money) I may refrain from putting a comp on it.