Uberti use the same diameter for all Magazine tubes, 45, 44-40 as well as .357 / .38. The Magazine Tube System get the 38 rounds from zig-zag into a straight line, and let them come out of the Magazine also straight into the carrier.
The aluminum tubes are anodized. The kit is coming with two different strength of springs.
Only available for 20 inch barrel length and shorter. The tubes must be shortened to fit.
While this kit is easily installed, it is not drop-in, it requires fitting by a competent Gunsmith.