I've been using Swissvax products for a while now. After getting the M5, I knew I was going to have to deep clean the interior. This is where the Swissvax leather care system comes in.
This is the more aggressive cleaner with a solvent added. It can be used for heavily soiled leather surfaces but I wouldn't use it all the time as solvents can age leather faster. You would use this in combination with the Leather Brush and then follow up with Swissvax Leather Milk.
I've found that the Interior Towel works really well with the Swissvax products.
It comes in two sizes: 250ml and 1000ml.