When he visited last month, the furnace/air conditioning tech casually mentioned that the filter, which generally lasts a year or so, had about another month of useful life. Any 16 x 25 x 5 filter would do, but a higher MERV rating would be better for an asthmatic.
Did you know that while the filter box may say 16 x 25 x 5, the size of the actual filter vary up to three-quarters of an inch - in any direction? The "actual dimensions" are also printed on the box, but in teeny tiny numbers. By pulling the old one out of the furnace, I could find the real size - 15 3/4 x 24 7/8 x 4 3/8, if you are interested.
This is why handymen charge an arm and a leg: nothing about home construction makes any sense.
The all-important MERV rating? MERV stands for "Minimum Efficiency Reporting Value".
I feel so much better informed, knowing that. Don't you?