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Description
Flowmonster Performance Muffler 3 in Dual inlet & outlet 12599-FM 409 StainlessOverview The Flowmonster series of absorption style mufflers deliver a moderate tone for the enthusiast looking for a deeper, more aggressive exhaust note than most OE (Original Equipment) mufflers, unlike the racey exhaust note associated with "chambered" style mufflers. Interior construction features 3. 50 inch "straight through" perforated 409 stainless steel tube surrounded by high temperature sound absorption packing material which helps to
Overview
The Flowmonster series of absorption style mufflers deliver a moderate tone for the enthusiast looking for a deeper, more aggressive exhaust note than most OE (Original Equipment) mufflers, unlike the racey exhaust note associated with "chambered" style mufflers.
Interior construction features 3.50 inch "straight-through" perforated 409 stainless steel tube surrounded by high-temperature sound absorption packing material which helps to deliver a deeper, mellower exhaust note. The internal design is reversible allowing the flexibility to be installed in either direction to best accommodate fitment with the intended vehicle. The fully MIG-welded 409 Stainless Steel material is embossed with the "FLOWMONSTER" logo on the case.
Interior construction features 3.50 inch "straight-through" perforated 409 stainless steel tube surrounded by high-temperature sound absorption packing material which helps to deliver a deeper, mellower exhaust note. The internal design is reversible allowing the flexibility to be installed in either direction to best accommodate fitment with the intended vehicle. The fully MIG-welded 409 Stainless Steel material is embossed with the "FLOWMONSTER" logo on the case.
Features:
- 409 Stainless Steel construction for superior corrosion resistance and good looks
- Interior construction features high-temp interior sound absorption material delivering a deeper, mellow exhaust tone
- Perforated High-Flow straight-through tube design for increased exhaust flow
- Moderate increase in interior tone over most OE mufflers
- A stainless steel performance muffler at an economical price
- Internal Design is reversible allowing flexibility to be installed in either direction
- Sold Individually
- This is a Universal Fit muffler - Not a Direct fit. Some adaption may be required for proper fitment on some applications
| Body Height (in) | 5 |
| Body Length (in) | 22 |
| Body Width (in) | 11 |
| Finish | Natural |
| Fitment | Universal |
| Inlet Connection Type | Pipe Connection |
| Inlet Inner Diameter (in) | 3 |
| Inlet Outer Diameter (in) | 3.13 |
| Inlet Position | Dual |
| Material | 409 Stainless Steel |
| Muffler Series | Flowmonster |
| Muffler Type | Absorption / Glasspack |
| Outlet Connection Type | Pipe Connection |
| Outlet Inner Diameter (in) | 3 |
| Outlet Outer Diameter (in) | 3.13 |
| Outlet Position | Dual |
| Overall Length (in) | 28 |
| Reversible | Yes |
| Shape | Oval |
| Sound Level | Moderate Sound |
| Type of Muffler | Absorption |
| Part Number | 12599-FM |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.3 ★★★★★
Based on 6 reviews
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Product Reviews
★★★★★ 4
Soft, Fluffy & Decently Supportive
Size: Standard (2 Pillows + 2 Protectors), Style: Soft, Configuration: Pillows + Protectors
These pillows are wonderfully soft and fluffy, making them great to sleep on.
They hold their shape well, especially if you get the version with a protective cover.
Comfort is good, and they moderately stay supportive through the night.
Overall, a great pillow pick that works exactly as expected.
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Reviewed in the United States on May 25, 2026
★★★★★ 3
Too firm
Size: Standard (2 Pillows + 2 Protectors), Style: Soft, Configuration: Pillows + Protectors
Too firm. Seems like there is too much filling inside the pillow. You can’t fold it in half or burrow into it. Otherwise the quality is quite good.
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Reviewed in the United States on October 9, 2025
★★★★★ 5
pillows
Size: Standard (2 Pillows + 2 Protectors), Style: Soft, Configuration: Pillows + Protectors
soft dont hold shape
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 20, 2026
★★★★★ 5
Excellent purchase
Size: Standard (2 Pillows + 2 Protectors), Style: Soft, Configuration: Pillows + Protectors
I purchased this Amazon Basics pillow set with protective pillow covers, and it was honestly a great buy. The pillows have a soft density, which is perfect if you like comfort without feeling too firm or stiff. From the first night, they adapted well to my head and neck, helping me sleep more comfortably.
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Reviewed in the United States on January 6, 2026
★★★★★ 1
Don't try to save $$ when buying pillows. Better to sleep happy!
Size: Standard (2 Pillows + 2 Protectors), Style: Soft, Configuration: Pillows + Protectors, Size: Standard (2 Pillows + 2 Protectors), Style: Soft, Configuration: Pillows + Protectors
Instead of purchasing what I was looking for I went with the Amazon variation and I'll think twice before doing that again. The reviews for this pillow said that it was "soft" (not FIRM) and good for side sleepers. Now imagine a pillow that you have to inflate, and you fill it to maximum capacity, then try to sleep on that balloon! It barely gives when you lay on it and is FIRM! Go with your gut and don't try and save a few bucks when you buy something as important as a pillow. Unfortunately they were vacuum packed and I don't think I can return them. They inflated quite a bit and it would be a pretty big hassle. Someone is getting a gift of 2 very firm pillows!
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Reviewed in the United States on April 28, 2025