Hi,
I had a look on the internet out of my own interest.
Apparently the dimensions are very similar.

This filter has
Height: 29.3 cm
Width: 20 cm

Your original filter for the Air Purifier 4 has
Height: 29.3 cm
Width: 21 cm

It is best to order the M16R-FLP-GL.
You are guaranteed that it will fit.

LG. Michi