Does this Saker grease couple REALLY work?

In this video, I'm checking out a grease coupler ($23!) that was sent to me a few months ago. This is a grease coupler that seals onto the zerks fittings and seals TIGHT. I was able to successfully grease 2 seized fittings on my Kubota bucket. Now I did have issues with the product not being able to fit into some spots.
Basically, if your zerks is covered by a shroud that's TIGHT around the fitting it might not work. For everything else, I would recommend the product. Here's a link to it below.
www.smartsaker.com/products/s...