The Prep Bible.
These two units fit different platforms. Read this as a line-vs-line breakdown, then pick the version cut for your own setup.
Trijicon HD Night Sights CA128Y is cut for the Colt 1911 Novak cut, with a yellow front sight, dovetail mounting, and a rear sight mounting location. It carries the HD model designation and is built with illuminated, shock proof features.
Trijicon Bright & Tough HK06 is built for the H&K USP platform as a 3-dot night sight set, finished in black with green tritium and the Bright & Tough model designation. It is also listed as illuminated.
Both are Trijicon handgun night sights with a green reticle color, but they differ in platform fit, model line, color, and listed features. The CA128Y specifies dovetail mounting and a rear sight mounting location while the HK06 does not list these aspects. The CA128Y is priced at $157.99 and the HK06 at $124.99.