TinySWR measures 0.6 X 0.8 inches square and was made to be installed inside of rigs like the KD1JV Sprints (in Altoids tins) and other super small QRP rigs.
The circuit board is available from OSH Park, a "community circuit board manufacturer". Barry N1EU has put together a list of the required parts, available here as an easy to order form from Mouser.
I no longer have my AT Sprint or MTR transceivers but this little circuit would easily fit into either of them and would provide the ability to trim or otherwise tune the antenna. Even with the popular PAR end-fed antennas that don't require a tuner, I never liked operating blindly, trusting that the SWR in a particular installation of the antenna was matched.
Confirmation of low SWR is always nice to have and the TinySWR would provide that.