I’ve been doing this for a while now. The sponge is just from one of those small sponge paint brushes that you get at your local hardware or dollar store. The point on the tip focuses the lube where it needs to be. Stored in a Altoids tin. Application is simply putting several drops on the tip and running it along the inside of the chain. Sponge is simply stored in the tin. The tin is NOT filled with lube and the sponge is not soaked in lube, or you will end up putting WAY too much lube on. This method actually saves a lot of lube vs. putting a drop link by link and wiping off excess. Coverage is also more uniform and if you do it right there is no excess to wipe off. It’s also way quicker.