An original P-53 ramrod is 39 inches long. The diameter of the ramrod should be pretty consistent from about an inch behind the tulip all the way down to the threaded end. Some of the ramrods being sold on e-bay are IMO Snider Mark III ramrods /cleaning rods. The Mark III is the Snider that was made as a Snider and not a converted P-53. In an effort to reduce weight, the Mk III cleaning rods were turned down starting about 4 or 5 inches behind the tulip. The turning was started in this area behind the tulip since the ramrod thickness was necessary to hold the ramrod in place against the brass stock nose cap which was still modeled after the P-53. This tapering of the ramrod results in a smaller diameter ramrod than a P-53 which is OK for the Mk III since it is a cleaning rod and not subject to the stress of ramming down a cartridge. This turned down ramrod will tend to rattle around in the channel when inserted in a P-53. An easy way to tell the difference between a P-53 ramrod and a Mk III cleaning rod from a picture is to look at the threaded end. A P-53 ramrod will be thicker than the threaded portion of the ramrod. There will actually be a small shoulder where the ramrod ends and the reduced diameter threaded portion starts. A Mk. III ramrod will be about the same thickness as the threaded portion without the shoulder.

Many of the Mk. III ramrods will also appear to have a tulip which appears to be slightly smaller and somewhat squared and not round. Another varient.

Hope this helps you out. I would never have known all this had not I bought a P-53 on line which was advertised as having an original ramrod and ended up getting the Mk. III rod instead.