Hello, I'm Shinji Yamasaki, the representative of Yamasaki Exercise Equipment Manufacturing. This equipment was researched and developed by me to strengthen the wrist strength necessary for arm wrestling and wrist wrestling. The product name is the [Wrist Strengthening Dumbbell Shaft]. When using this equipment, I think it's great to train with your elbow on a table, just like when you arm wrestle, as it gives you a more realistic training experience (see images). Images (A, B) show wrist curls with the palms facing up. Images (G, H) show wrist curls with the thumbs facing up. Images (I, J) show training by twisting the wrist inward. Image (C) is the [Wrist Strengthening Dumbbell Shaft]. Images (D, E, F) show the plates set on the [Wrist Strengthening Dumbbell Shaft]. As you can see in the images, even with the same weight plates, the load on the wrist changes between (D) and (E); (E) has a greater load. "Since the muscles of the forearm move the wrist, this equipment is also ideal for those who want to make their forearm muscles thicker and stronger. The grip diameter of this equipment is 35mm. Plates with a hole diameter of 28mm are recommended." (Note) ... "Plates are not included with this product." [Additional Information] Arm wrestler Hiroshi Kotera (6-time All Japan Championship winner, World Championship 55kg class winner, and the first Japanese winner of the 2019 World Cup) shows various training methods using our [Wrist Strengthening Dumbbell Shaft] on Instagram. If you are interested, please access Instagram and search for "Hiroshi Kotera" or "hiroshi_kotera". I invented the [Wrist Strengthening Dumbbell Shaft], but Mr. Kotera skillfully used the [Wrist Strengthening Dumbbell Shaft] in ways that I, the inventor, had never even thought of, so I was honestly surprised and learned a lot, thinking, "Wow, I see, there's also this way of using it!" (＾０＾) (Note) ... Products from "Yamasaki Exercise Equipment Manufacturing" are only sold on the "Yamasaki Exercise Equipment Manufacturing" website, Mercari, and Yahoo Auctions.