The Pro Seal works great guys. 15 bucks. No Toil is also great, Don. Couple minutes, at most, in the sink, the filter looks brand new. Its a biodegradeable powder cleaner that really knocks it out quickly. Also, I think their cleaner is easier on the foam material, so the filters last a long time. The Pro seal is like a dense foam rubber. Its very sticky on the airbox side, and on the filter side. Now its a bummer to grease the couple bikes we have without the pro seal. It does not leak. With just filter oil to the seal. When filter is removed the Pro seal is still looking brand new. Had them for over 4 years, with No Toil, very happy.
Also, just read that the No toil cleaner does not disolve the seam-glue of air filters, like petroleum products, so they stay in one piece. Saves time, money and parts, can't go wrong with it.