Handy little tool to get seizure or wear marks off the cylinder wall.
Easily done -even possible with portable electric drill- and a 5 minute job. Move the tool slowly up and down the cylinder to get a nice cross-grinding pattern again.
If there are spots on the piston as well -and they are not too heavy- then you can use abrasive paper (400) for removing those. But be careful to remove those parallel to the piston rings.
The delivery contains a set of spare stones.
Attention: Be careful with cylinders which have large cut outs at the cylinder bottom for the transfer ports. Otherwise the grinding tool can get stucked in.