A couple weeks ago I saw some Tue/Wed pictures from a tour event, and a couple of players were on the practice green with this putting aid I had never seen.
The whole setup as seen above runs for $140. The white "perfect putting line" alone costs $50. I'm usually not one for putting aids, and have usually just stuck two tees in the ground as a small gate, but I was bored as hell today and decided to make my own Perfect Putting Aid.
It's 4 feet long, and the two gates at either end are different sizes, one is larger, the other has about 1/8'' clearance on either side when a ball is passing through. Final cost was about $1 for the dowel rod since I had some scrap MDF in the garage. Plus it all comes apart in fits in my bag and I can use the dowel for alignment at the range.