The valve is the same OD as an MRod valve (and 4.25" long), but the ports are bore-size (actually, slightly over 0.257") on the outlet and huge (2.5X bore area) on the inlet side.... so the effective volume of the valve is the entire reservoir, 400cc.... In addition, there are no 90* turns in the ports, the throat of the valve is well radiused where it blends into the exhaust port, which then turns 30* into the 17/64" transfer port, and then another 30* turn into the port in the receiver, which will then blend into the barrel though an oblong port measuring 3/16" wide x 5/16" long, with NO bolt probe in the way.... The valve throat is 5/16", sealed by a 3/8" PEEK poppet on a 1/8" stem, so the throat area is 24% greater than the bore area.... You will notice that my airgun building (shop time) happens in the winter when the Motel is pretty much dead.... *LOL*.... For the rest of the year I just spend all my spare time thinking....Bob