A-Premium Stretch-Fit Serpentine Belt 31.73 in — 4-Rib K-Section for Subaru 2.5L AC

The A-Premium Stretch Fit Air Conditioning Serpentine Belt is a 31.73-inch, 4-rib EPDM drive belt engineered to replace the air conditioning compressor belt on compatible Subaru 2.5L H4 engines.

This stretch-fit serpentine belt is designed for a precise fit in specific Subaru models and trims, offering EPDM construction and polyester cord reinforcement for long-lasting durability. Because it’s a stretch-fit style, the belt measures shorter at rest and requires a tensioning tool for installation; once fitted it self-tensions for consistent operation. The belt’s K-section 4-rib profile matches factory routing for the air conditioning compressor on select Forester, Impreza, Outback, WRX, and WRX STI vehicles with 2.5L H4 engines.

Which vehicles and engine locations does this belt fit?

This belt fits many Subaru vehicles equipped with 2.5L H4 engines where an A/C compressor belt is specified. Confirm vehicle year, engine code, and VIN details to ensure compatibility before ordering.

• Subaru Forester 2009–2011 H4 2.5L; Forester 2012–2013 H4 2.5L (Turbo)
• Impreza 2008–2014 H4 2.5L; Outback 2008–2011 H4 2.5L (VIN 4th digit G)
• WRX 2013–2016 H4 2.5L; WRX STI 2013–2021 H4 2.5L
• Designed specifically as the air conditioning compressor drive belt (gasoline engines)

How is the belt constructed and what are the key measurements?

This A-Premium belt uses EPDM rubber for improved resistance to heat, ozone and wear, combined with polyester cords for tensile strength. It follows the K cross-section standard and provides a 4-rib profile to match factory pulleys and tensioning geometry.

• Effective length: 31.73 inches
• Outside circumference: 32.25 inches; top width: 0.56 inches
• Rib count: 4; cord material: polyester; belt material: EPDM
• Cross-section designation: K (stretch-fit design)

What does 'stretch fit' mean and how do I install it?

Stretch-fit belts are manufactured slightly shorter than their installed operating length and rely on a tensioner tool and the vehicle’s pulley arrangement to stretch into place. After installation the material relaxes and maintains correct tension, removing the need for manual retensioning.

• Requires a dedicated tensioning tool or installer experienced with stretch-fit belts
• Appears shorter when not mounted—do not trim or force onto pulleys
• Self-tightens once routed and released, providing consistent tension
• Installation Location: air conditioning compressor (gasoline engines only)

Are there part numbers and warranty details I should know?

This belt carries multiple reference numbers used across Subaru OEM and aftermarket catalogs, making cross-referencing straightforward. A-Premium supports the product with a limited warranty to help protect buyers against manufacturing defects.

• Reference numbers include K040317SF, 11718AA080/081/082, 23979AA000
• Also equivalent to part numbers 4PK805 and 4PK805 SF
• One-year unlimited-mileage guarantee from A-Premium
• Sold as a single A/C compressor serpentine belt for specified vehicles

Who is this for? If you own one of the listed Subaru models with a 2.5L H4 engine and need a reliable replacement for the air conditioning compressor serpentine belt, this A-Premium stretch-fit K-section belt is built to match factory fitment and long-term resistance to heat and corrosion. It’s a suitable option for professional technicians and experienced DIYers who have access to the proper tensioning tool and who want a direct-fit aftermarket alternative backed by a one-year guarantee.