The Ultradot sights are good, They are popular among serious bullseye competitors who would spend more money if they thought something else would give them an advantage, so that speaks well about the quality. However, nothing about an Ultradot Matchdot is low profile. They are relatively large and heavy as far as red dot sights go.
If you just meant low profile in terms of the scope rings, then other posters have given good advice. But if you want your whole sight setup to be lower, smaller, and lighter, then there are other options. The king of small tube style red dots are the Aimpoint micro series. These sights are expensive, but you get what you pay for. Aimpoints are popular on duty rifles that will be carried into the toughest conditions. They are also very good optically.
For a moderately priced sight with a form factor similar to the Aimpoint, I have been satisfied with sights from Primary Arms. I have a basic model from Primary Arms that cost about $100 and I think it is a good value. I would not hesitate to put one on any pistol I wanted to shoot accurately.
For a more medium sized setup, I also think the 1 inch tube Ultradots are very satisfactory. They are a bit smaller than the 30mm Matchdot, but larger than the micro sights. Of course, none of these smaller sights have the adjustable dot size of the Matchdot. I don't find the adjustable dot size to be that useful, but some shooters strongly prefer it, so that is a matter of personal preference.
