Is this HEPA filter compatible with the Shark NV352 vacuum and why do some reviews say it doesn't fit?

Short answer yes. The NV352 uses the Shark Navigator 350 series filters which are the pre motor set XFF350 and the rectangular HEPA XHF350. Most of the scary reviews come from two things. Some third party HEPA frames have a slightly thicker gasket so the grille feels hard to close the first time but it does seat once the gasket compresses. Others accidentally try to fit a different series filter or leave the old gasket or felt in the cavity which doubles the thickness and makes any new one seem wrong.

If you want a quick way to sanity check dimensions the HEPA for the 350 series is roughly 5.3 by 4.6 inches across the plastic frame and about 1.2 inches thick including the soft gasket. Measure the inside of your front HEPA grille and you should be right in that ballpark. As long as the set says XFF350 and XHF350 you are matching what Shark spec'd for NV352 even if your old foam looks a little different because Shark changed the mold over the years.

I would go with 4 Foam + 2 HEPA for Shark NV350 NV352 since it includes both the XFF350 pre motor filters and the XHF350 HEPA so you refresh the whole system at once and avoid a mismatch.

I have this exact model and ran into the same worry when the foam frame looked different. The new HEPA was the XHF350 rectangle and it did fit my NV352 once I removed the thin felt ring that stayed behind from the last filter. My grille measured about 5.3 by 4.6 inside and the new filter with gasket was near 1.2 thick. I thought it was wrong and almost sent it back but then I pressed the door closed and it molded in after a day. Works great.

I service these often and the NV352 takes the 350 series rectangular HEPA with no drama. Visual differences in foam color or the rib pattern on the frame do not matter. The spec does. Look for XHF350 on the HEPA and XFF350 on the pre motor set.

Quick checks I do in the shop. Confirm the door opening is around 5.3 by 4.6 inches remove any old seal stuck in the cavity, and close the door with steady pressure the first time. If it is still fighting you, pull it back out and make sure the filter is fully seated and not riding up on the edge of the recess.

NV352 takes the Navigator 350 series set so the rectangular HEPA marked XHF350 is the right match. The frame is about 5.3 x 4.6 inches and roughly 1.2 thick with the soft gasket. If your front grille opening is in that range, you are good. Tight the first time. Then fine.

If anyone says it does not fit, the usual culprits are a leftover felt or rubber ring still stuck in the cavity or a fresh gasket that has not compressed yet. Pull the old ring if present, seat the new filter square, and close the grille with even pressure. It beds in after a couple uses.

Short answer is yes. NV352 shares the 350 series pre motor set XFF350 and the rectangular HEPA XHF350 so yeah... the plastic frame on the HEPA is roughly 135 x 117 mm and the overall thickness with the gasket is about 30 mm. That matches the grille recess on the front of the NV352.

Most misfit reviews trace to a double stacked seal or people mixing series by accident. If you measure the inside of your grille and you are close to 5.3 by 4.6 inches, you are in the right family. A firm first close is normal because the gasket is fresh foam and needs to take a set.

Measure the inside of the filter door lip to lip; you should get about 5.3 by 4.6 inches and roughly 1.2 inches depth including the soft rim, which confirms the right size... Before installing, remove any leftover felt or rubber liner, seat it flat, latch the door, and recheck after a couple runs as the gasket compresses.