The Kellermann chain tool KTW 2.5 

Replacing a worn chain has never been easier with the DIY Kellermann chain tool KTW2.5. It allows easy removal of the worn chain and a precise assembly of the new chain with hollow rivets so that they can stay installed. The tool is designed for chains of all brands (such as DID, Regina, RK, etc.). The tool now comes with two arbors for different diameters. The pre-installed arbor is now stronger and works for 5xx and 6xx chains.
The additional arbor especially works for 4xx chains. For use, only a 19mm ring or socket wrench is required.

The chain tool contains a patented, magnetic positioning tool for the assembly of the connecting link, which ensures simple and absolutely precise mounting of the side plate of the connecting link. The positioning unit consists of two magnetic plates that are coupled together via a guide. This design allows precise and comfortable positioning of the parts of the connecting link. The plates stick magnetically to the connecting link, so you have your hands free to work.

See the tutorial video.