Possibly the most common cap seen during the war, and the most underrepresented cap among reenactors.  This classic dumpy Hoff and Company cap will work for most any US impression and will be made by Conor Timoney to match an original exactly.  Artillery cap brass is available as an add-on option.  From Conor:
 
“The caps of George Hoff and Company of Philadelphia represent some of the cheapest and most hastily produced caps issued to Union soldiers during the entire Civil War. From the firms first contract in 1861 for 20,000 forage caps to its last in 1864 for a whopping 200,000, Hoff and Company produced the most forage caps of any forage cap Contractor surpassing even the famed Lewis James and Isaac Phillips. In the year 1864 alone, Hoff produced over 550,000 caps.
The pattern of these caps is generally typified by a 5” disc, a short 4 - 4 3/4 inch body, a generously rounded base and thin, wavy and unreeded welts. Lacking the reed or any filler, this often allows the body to creep up around the disc to created a recessed look similar to a kepi. The visors on these caps are invariably cut quite shallow along the inner edge so as to slant down at an extreme angle. This has caused many collectors to incorrectly label these caps as “McDowells” however the visor does not press quite as firmly against the forehead nor is it anywhere near as crescent shaped to warrant such nomenclature. The sweatbands on these caps are also quite frequently stitched and turned over resulting in a lack of any visible stitching, save for the tacking stitches along the inner edge. This often results in the sweatband being visible form the outside when worn and presents a somewhat welted appearance along the bottom edge of the cap. The chinstrap is also of note as they frequently feature rounded ends as opposed to squared.
While the pattern of Hoff caps varies little, the materials show a wider variation than just about any other contractor. Hoff caps have surfaced cut from broadcloth, flannel, kersey and even over dyed green facing cloth for issue to the 1st and 2nd US sharpshooters. The linings vary considerably as well as they seem to exhibit silesia, polished cotton, plain cotton and even linen in everything from black to tan. The sweatbands too vary and appear embossed, plain, enameled and in a variety of colors congruent with the linings.
While possibly the most unsightly cap ever produced, Hoff caps are perhaps the most underrepresented cap in living history. In many cases, their reproduction has been over engineered to produce caps too well constructed to resemble anything close to the real thing."