Our ACs are Coleman so I don't know if Dometic is similar. However, we converted our filters to the square pleated filter used in a standard furnace. We chose a MERV rating of 13 (MERV rating is 1 - 16 with higher number stopping smaller particulates) Since they are pleated the actual surface area is increased to enable proper air flow volume while providing better filtration. My AC coils are very clean as a result but we change them every 3 months.