The HE509T is essentially a pistol-sized optic, but like most mini red dot sights, it can be used across a wide variety of firearms.
What kind of quality can you expect from a Red Dot Sight that costs less than $350? Read Pike's review of the HS510C to find out.
You rarely see a compact red dot sight for a sub-compact pistol like you would with that full-size pistol. However, Holosun now offers two electronic sights that are small, rugged, reliable, and reasonably priced (according to them).
Holosun may have started small, but somehow the company exploded into the market and ended up producing the Holosun 507C: a mini red dot that challenges the Trijicon RMR. Read Pike's review.