MT3 ABS keycaps have a noticeable texture. It is rougher than the "textured" finished that Signature Plastics uses. Let alone the "smooth" texture that are used in many SA sets. (FYI Signature plastics mentions a polished texture as well, but I've never seen this in the wild. But I digress.)
Some time ago a fellow drop member posted this image comparing SA and MT3. Hopefully you find it useful.
Mt_MechYes, unless HyperX has a different bottom row layout like Razer used to have, but I've used HyperX caps on one of my boards before and they fit fine so I'm fairly sure they have a standard bottom row.
Use this interactive website to compare MT3 with many other profiles - https://www.keycaps.info/This overlays two of @voodoo6k 's pictures to show MT3 vs SA:
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This is Keyreative's comparison of SA, KAT, and Cherry (GMK):
ABS(acrylonitrile butadiene styrene) is a thermoplastic that is the principle compound in this and the majority of keycaps on the market. As a material it is reasonably tough and resistant (used to make LEGO blocks), and can be made in to a wide varity of colors.
The term doubleshot means that the keycaps are made in a two step process. The legend (aka the letter, number or symbol) is formed in a mold. Then the resulting plastic part is then placed in a second mold and a contrasting color is then molded around it. This a finiky and time intensive process. However the end results is a very durable keycap that will never have the legend worn off with use.