Do NOT use them for Al sludge filtration! Al sludge MUST be filtered through paper, repeatedly, because it will clog them in seconds!
Or - you can use a centimeter or two of Celite in any kind of filter funnel. If the filtration slows down, scrape the Celite surface carefully to expose a "new" unclogged surface (but never as deep as to touch the filter), increasing the filtration speed again. Wash the filter cake with IPA or THF, then remove all the sludge, taking care not to take too much of the celite with it, boil the sludge in some IPA for a few minutes, then filter it all again. Rinse cake with THF or IPA. This to ensure that no product stays attached to the Al sludge.
The same general procedure can very successfully be used with Lithium Aluminum Hydride post-reaction sludge after it has been decomposed with IPA and aqueous NaOH solution as described in https://www.thevespiary.org/rhodium/Rhodium/chemistry/lah.reduction.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/lah.reduction.html)