This compact chain tensioner may be small but it is top quality, like everything made in Japan by Mikashima.
Although designed for Keirin track racing, the ease of use makes them perfect for your street bike.
These fit most steel track frames having dropouts up to 5mm wide and are available in two versions - one adjusts using a 3mm allen bolt and the other uses a 10mm hex head bolt. Both versions are NJS stamped.
Not sure how thick your dropouts are? Don't take a guess. Measure them!