Standard Polypak® Rod/Piston U-Seal 4.250

Standard Polypak® Rod/Piston U-Seal 4.250" x 5.000" x 0.375" - AU/NBR

Marsoni

M251S

$75.02

Get it in 3 business days with 1 day shipping. Friday, May 29

Standard Polypak® Rod/Piston U-Seal 4.250" x 5.000" x 0.375" - AU/NBRProduct Details : Standard Polypak Rod Piston U Seal 4. 250" x 5. 000" x 0. 375" AU NBR Part No: 37504250 4615 Product Category: Symmetrical Seals Product Type: Rod Piston U Seal Profile: Standard Polypak Material(s): Polyurethane Nitrile Material Code: AU NBR Temperature Range: 65F to +200F ( 54C to +93C) Pressure Range: 5000 PSI ( 345 Bar) Surface Speed: < 1. 6 ft s (0. 5 m s) System Of Measurement: Inch Dimensions: 4. 250" x 5. 000" x 0. 375"

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MUCH better than the cheap plastic OEM part, Just a reminder though, these thread into an aluminum block so be very careful to start them finger tight first, then evenly tighten both bolts to push the fitting into the chamber. If you don't, it will slightly misalign and you run the risk of stripping the threads. The one comes with the replacement o ring, and be sure to get some antifreeze on that seal prior to attempting to push it into the chamber. IT IS A TIGHT FIT, but that's what you want, so just be careful. You might also want an extra hose clamp on hand, as the one that came with this began to bend as it got tight, so I had to replace it for peace of mind. Overall, great product though.

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Reviewed in the United States on January 9, 2026

Verified Purchase

Dklnyc

Natrona Heights, US

★★★★★ 5

Strong product

Great quality

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Reviewed in the United States on March 11, 2026

Verified Purchase

Sebastian Benavides

Dallas, US

★★★★★ 1

Snapped bolt

I tried putting it on my n55 from a m235i and it did not fit properly. I was in a rush to try to put it on and thought it was on properly and I thought it did. And I snapped the bolt because the bolt because it was not aligned after I looked at harder I do not recommend for a n55. do not get this cheaply made pos. I recommend getting it from fcp euro where parts will actually fit and not fail.

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Reviewed in the United States on January 1, 2026