Filter for RX2-B and RX is Different

These two comptible Hitachi filters look the same right, but in fact, they are not.

The most obvious difference lies at the bottom. The RX filter bottom is flat with a hole in the middle; while the RX2-B one is not.

Take the bottom aside, when we install the filter, we will find that the in-let/out-let diameters not the same either. The diameter of RX2-B is slightly bigger than RX.

When we flip the filter, we will notice the filters are with different shapes too.