Okay, let's see what I can do here.
Firstly, the Spectre has two finishes - plain black, and black with a circuitry pattern on it. Plain black is the closest match to the show's hilt, and I'll refer to that in the description. All descriptions, directions etc. are based on having the activation switch at the front of the hilt i.e. facing you. Unless otherwise noted, all pieces have a plain silver finish.
The length given in the site description is 13.5 inches, emitter tip to pommel base, and 9.75 inches from the guard to the pommel base. The hilt is 1.5 inches in diameter, which I believe is pretty standard for US hilts, and the guard is 2.9 inches around.
The pommel is about 2 inches from the base to the seam with the hilt body. The lower half is a flattened cone with a slight inward taper and a flat top (the pommel base) with 4 arrowhead-shaped holes in it forming the corners of a square pattern. The upper half of the pommel is a ring slightly wider than the cone with 4 slim rectangular ridges at each quarter point.
The main body of the hilt is about 8 inches long. It is predominantly a flat black with a silver sleeve covering the rear half. The sleeve has collars around the top and bottom of the body, with the pommel-end collar being a slim ring, and the emitter-end collar being thicker, perhaps an inch or so wide. The emitter-end collar has a silver knurled thumbscrew protruding from the front, just above the activation switch. There appear to be gold accent screws flush with the surface of the collar at 90 degrees to the left and right of the thumbscrew, but I can't find a picture that shows these clearly.
The sleeve, as noted, covers the rear of the body of the hilt. There is a silver covertec wheel at the pommel end of the sleeve. The sleeve is otherwise lined from collar to collar with what appear to be vents showing the black body of the hilt under the sleeve. There are six of these, evenly spaced around the diameter of the sleeve. They appear to be about as wide as a pencil eraser. I assume they're vents rather than just lines, but as I've not held one and they're not mentioned in the written description I can't say for sure - Emory's video may cover this:
https://youtu.be/d_XJPyEtrq0 or someone else can likely confirm.
The activation switch is set into a box like that on the Emperor's Hand - you can either have the tombstone shaped box, or the rectangular box. Each is about 1.5 inches long, with an AV switch sitting in the centre.
At the top of the hilt is the emitter, which at its base features a wide circular silver guard approximately twice the width of the hilt. This isn't particularly thick, perhaps as much as a thick coin, but I'm sure it's sturdy enough.
The emitter is more difficult to describe as it's quite involved, so hopefully this makes sense. Above the guard is a recessed black neck section, perhaps half an inch wide. Above this is the main part of the emitter, about 2-2.5 inches high. The emitter itself is enclosed in another sleeve, with the emitter projecting about half an inch beyond the lowest part, but the sleeve then sweeps upwards so that the highest part is about a further half inch above the lip of the emitter - think of this as being like an open, turned up collar on a dress shirt, if that makes it clearer, but I'm afraid it's not an easy arrangement for me to describe!
The emitter sleeve can be left plain, or have 13 vents inserted with a low rear central vent and then 3 pairs moving outwards of increasing height, followed by 3 pairs of decreasing height - the longest looks to be about an inch long, and they're about as wide as the guard is thick. Just above the tip of the central vent, about halfway up the rear of the emitter, is a hole to which a covertec wheel can be attached.
On the front of the emitter, below the lowest point, is a rectangular ridge that aligns with the thumbscrew, and activation switch. This is about an inch high, and perhaps a quarter inch wide.
As Zren Tobas and Infinit01 have noted, a D-ring on the pommel and covertec wheel on the emitter would most closely match the setup Kanan uses in the show, where he wears the emitter as a separate piece to hide his ownership of a lightsabre. I would also leave the emitter unvented, and have the body in black rather than with the printed circuitry pattern.
Hope that helps, it's a fairly complex design, mainly around the emitter.
