5L Belt Guide - Dimensions, Applications & Sizes

The 5L series is a Fractional Horsepower (FHP) V-belt measuring 21/32" wide x 3/8" tall. 5L belts are designed for medium to heavy-duty applications on equipment such as riding mowers, snow blowers, air compressors, and industrial fans. As the largest belt in the FHP "L" family, the 5L delivers reliable power transmission where smaller 3L and 4L belts fall short.

5L Belt Specifications

Specification Value
Top Width 21/32" (16.7mm)
Height 3/8" (9.5mm)
Belt Angle 40°
Min Pulley Diameter 3.5" (4" recommended)
Length Range 20" to 100"+ (outside circumference)
Construction Rubber with polyester cord

Understanding 5L Part Numbers

5L350 = 5L belt, 35.0" outside length.

The number after "5L" is the outside circumference in tenths of an inch. Divide the digits by 10 to get the belt's outside length in inches.

  • 5L250 = 25.0" outside length
  • 5L350 = 35.0" outside length
  • 5L500 = 50.0" outside length
  • 5L780 = 78.0" outside length

5L Kevlar Belts (K Suffix)

5L belts with a "K" suffix (e.g., 5L350K) feature aramid/Kevlar reinforced cords instead of standard polyester. Kevlar 5L belts offer:

  • Higher heat resistance for enclosed or high-temperature environments
  • Greater tensile strength and longer service life
  • Superior resistance to stretching and wear
  • Ideal for demanding outdoor power equipment and industrial applications

If your original belt fails prematurely due to heat or heavy loads, upgrading to a Kevlar 5L belt is a smart investment.

Common Applications

5L V-belts are found on a wide range of medium to heavy-duty equipment, including:

  • Riding mower decks – deck drive and blade engagement
  • Garden tractors – transmission and PTO drives
  • Snow blowers – auger and impeller drives
  • Air compressors – motor to pump drive
  • Industrial fans – blower and ventilation systems
  • Pump drives – water pumps and irrigation equipment
  • HVAC equipment – furnace blowers and condensers

5L vs B Belts – What's the Difference?

5L and B belts share the same 21/32" top width, which causes frequent confusion. Here are the key differences:

Feature 5L B
Top Width 21/32" 21/32"
Height 3/8" 13/32"
Measurement Method Outside length Inside length
Part Number Example 5L350 = 35" outside B33 = 33" inside
Grade FHP (light/medium duty) Industrial (heavy duty)
Interchangeable? Similar width, but B belts are taller and ride deeper in the pulley groove. Not a direct swap in all cases.

Tip: If you're replacing a B belt with a 5L (or vice versa), always verify the pulley groove depth and required length conversion. A B33 belt is approximately equivalent to a 5L360 in total length.

How to Measure a 5L Belt

5L belts are measured by outside circumference (the distance around the outer surface of the belt). To measure:

  1. Wrap a flexible tape measure around the outside of the belt
  2. Note the total circumference in inches
  3. Match to the nearest 5L part number (e.g., 35" = 5L350)

For a detailed guide with diagrams, visit our How to Measure a V-Belt page.

Ready to find your 5L belt?

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Popular sizes: 5L250, 5L350, 5L400, 5L450, 5L500, 5L550, 5L600, 5L700