My first review was due to my ignorance as the vertical plate didn't fully fit the tilt of my Sirui AM-5V. Yes, there is a slight difference in the size of the vertical and horizontal (smooth) plates, but when I found that I could open the AM-5V clamp after locking the lever, this wepoto works great. It's lightweight, adjustable, durable and perfectly finished. My apologies to Revain and Wepoto for my return/exchange, initial negative feedback and ignorance!