Professional product - Not for do it yourself use.
Use ONLY white applicators.
Confirm any leather is standard durable finished leather and not a "weak dye" leather material that can be easily damaged.
Note: Currently there are a variety of leather materials with a variety of top layers dyes on them used by many auto manufacturers. It is not possible to acquire or test this number of surfaces therefore user must confirm viability of any leather product and use at their own risk to avoid possibility of staining a "weak dye" material.