Excerpt: I purchased the Nikon HB-4 to use on a Nikon 20mm f2.8 lens. I could not be happier with this choice. It fits the lens extremely well while staying very compact for carrying. I am very happy with it.
Pros: Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight, Rugged, Strong Construction
Excerpt: After 10 years of owning the 20mm 2.8 Nikon lens I finally bought the hood. It good but sometimes it doesn't stay in place. It's just a twist lock and doesn't have any real locking system so it will sometimes come off if it's bumped. It's a little smaller than I thought it would be. Helps a little to keep the flair out of the lens from side angles. 50/50. Good about half the time. I'd still buy it as it doesn't take any room in the bag.
Excerpt: I bought the Nikon version of this hood (vs independent brand) expecting the best fit, but was disappointed to find that I could not get this hood in place with a reasonable amount of force. While the 20mm AFD is quite a well-made lens, I was afraid to twist the hood any harder onto the bayonet mount fearing that the lens barrel might come out of alignment.