"That is a common fuel filter for a fuel oil heating system. They are 10 micron."
Plus 1 to Jay - these are not sensitive to orientation much as the filter media itself takes up over 90% of the cavity. The 'top' and 'bottom' of the filter media is directly pressed upon each end and the filter 'open spaces' are small and 360 degrees around the filter perimeter -so you should be fine as long as you can easily prime the system.
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