What You're Actually Buying
This is a flex coupling section - corrugated stainless braid construction meant to absorb engine movement and vibration without cracking the pipe on either side of it. On the C500 it sits in that stretch of exhaust where a rigid pipe would just fatigue and split within a year or two.
4"-5" refers to the diameter range it's built to mate with - you'll still need to check your existing pipe ends and any step-down fittings before you order. Stainless was chosen here because mild steel flex sections rust through from the inside out faster than anyone likes to admit.
This is an aftermarket stainless replacement, not a Kenworth or PACCAR-branded part, but it's built to the same physical dimensions as 21533396 so it drops into the same location doing the same job.
Reading the Cross-Reference Numbers
The numbers in the table - PN-3-B-023, PN-3-B-038, the M66-7091 series, Dinex 8CE004, Volvo 21533395 - all trace back to the same physical flex section because Kenworth and Volvo share exhaust architecture on a lot of these truck lines going back to the mid-2000s. Volvo's 21533395 being one digit off from our headline number isn't a coincidence; it's the same part sourced under a different badge.
Where guys get burned is assuming any 4"-5" flex pipe on the shelf is interchangeable. Overall length, the flange or clamp style on each end, and how much corrugation is in the flex section itself all vary between builds even when the diameter matches. A pipe that's an inch too long or short will bind and crack again in six months.
Rule of thumb: pull the number off your old flex section or look it up by VIN before ordering. Don't go by truck year alone - running changes happen mid-model-year more than people expect.
Ordering From PartStop
We're in Tacoma and if you're local, this ships same-day when it's in stock - useful when a truck's sitting in the yard instead of running a route. Nationwide shipping if you're not close enough to walk in.
Every flex pipe we sell carries our 6+ month warranty. It's a stainless part doing a hard job near the manifold, so if it fails from a defect inside that window, we handle it.
Call or email us the VIN or the number stamped on your old flex section before you check out. Takes five minutes and saves you a return shipping hassle if the diameter or length doesn't match.
21533396 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 21533396. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cross-Reference | PN-3-B-023, PN-3-B-038, M66-7091-0320, M663541, 663542, 6665410320 |
| Dinex | 8CE004 |
| Volvo | 21533395 |
Frequently asked questions
Does 21533396 fit my Kenworth C500?
It fits the C500 in the 2007-2015 range, but confirm with your VIN or the number on your old flex pipe first - running changes happened within that span and we'd rather check than have you reinstalling twice.
Is this the same as the Dinex 8CE004?
They cross-reference to the same physical flex section and mounting dimensions, but Dinex is a different manufacturer building to that spec - not a Kenworth-branded part. Compare your old part's length and end style before assuming a straight swap.
Why does the Volvo number 21533395 show up in the cross-reference?
Kenworth and Volvo share exhaust component sourcing on a number of models from this era, so the Volvo-branded piece is functionally the same flex section under their part numbering. Still worth confirming by VIN since Volvo's own application list may differ slightly.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.