The flange unit of this bearing is made to oval shape, with two mounting bolt hole, which makes it for even easier installation.  The main advantage of this unit is it needs less space for installation, and specifically suitable where mounting space is limited.  Oval flange units are often used where a situation that there are two shafts installation and it is technically necessary to minimize the distance between the two shafts.  Oval flange unit mounting hole is basically conforming to square flange unit mounting dimension at the diagonal position of holes.