That clarifies a lot. So when they talk of "H tubes" they mean their model H (for Hiroshima) nixie tubes which are huge (height 135mm) compared to their previou

That clarifies a lot. So when they talk of "H tubes" they mean their model H (for Hiroshima) nixie tubes which are huge (height 135mm) compared to their previous model R or R|Z568M (for "resurrected" German Z568M from the 1970s; height 50mm I believe) that they produce for sale. https://www.daliborfarny.com/project/rz568m-nixie-tube/ https://www.daliborfarny.com/project/rz568m-nixie-tube/