With the Brass keels, you can precisely mark the ball. A very usefull accessory for referees who need clean the balls
How to clean brass?
Start with hot, soapy water and a microfiber cleaning cloth: Go over all of the surfaces thoroughly with the cleaning cloth, using a clean toothbrush to get into any crevices. Rinse with warm water and dry thoroughly.
Regular cleaning and polishing with a microfiber cloth will help keep dust and dirt from accumulating and keep your brass accents lovely and lustrous.