MagHolders are a great way to conveniently and comfortable carry your spare magazine. The horizontal orientation makes keeps your magazine inline with your belt so you dan't have your baseplate digging into your side. With a little practice you will find MagHolders make for a very fast and efficient reload as well. MagHolders are oriented with bullets down for the hand you will be drawing with (a right handed shooter will typically order a left hand MagHolder to be drawn with he left hand). If you prefer a bullets up orientation you will order for the same hand you shoot with and run your MagHolder upside down.
Love my Mag Holder! I have been using them for many years now. Great design. It is the only mag holder I use.