A Common Question We Get: "I ordered a PJ belt but only received a very thin, single-rib belt — where's the rest of it?"
This is one of the most common misunderstandings with PJ belts. Many industrial PJ belts are sold per rib, while customers often assume the product photo shows the complete multi-rib belt they'll receive. If you check the listing, you'll usually see it's priced with Unit: Rib — not "per belt." See the range here.
What Is a PJ Belt?
A PJ belt is a type of Poly-V (Micro-V) belt with small V-shaped ribs running lengthwise along the belt.
· P = Poly-V
· J = J-section rib profile (2.34 mm rib pitch)
· The number in the code = belt length in millimetres
For example, 610PJ means:
· 610 mm outside length
· J-section rib profile
· Sold by the rib in most conveyor applications
Difference between Flat Belts, V Belts and Poly Ribbed Belts
Flat belts use friction on a smooth pulley surface and are best suited to light-duty, high-speed applications. V-belts improve grip by wedging into pulley grooves, allowing greater power transmission. Poly-V belts combine the flexibility of a flat belt with the traction of multiple V-belts, making them ideal for compact, high-speed drives where efficiency, smooth operation, and space savings are important. PJ belts are one of the most common Poly-V belt profiles used in conveyor rollers and other compact drive applications. See RR Fishers range of belts here.
Is a PJ Belt the Same as a J Belt?
Yes. "PJ" and "J" refer to the same rib profile — the difference is just whether the belt is measured in metric or imperial units. Belts made to metric standards use the "P" prefix (PJ, PK, PL, PM), while the same profiles measured in imperial/inch lengths are labelled J, K, L, and M. So a PJ belt and a J belt have identical rib geometry and pitch — only the length numbering system differs. If you're cross-referencing a belt from an overseas catalogue or an older machine, don't assume "J" and "PJ" are different products; check the actual length and rib count, not just the letter prefix.
· H (PH): 1/16 inch (1.6 mm) rib pitch— specialty applications for smaller drives
· J (PJ): 3/32 inch (2.34 mm) rib pitch — fractional-horsepower applications, especially in consumer goods such as appliances and power tools
· K (PK): 9/64 inch (3.56 mm) rib pitch — developed for automotive applications, especially serpentine configurations. Find PK Belt range here.
· L (PL): 3/16 inch (4.70 mm) rib pitch — industrial applications
· M (PM): 3/8 inch (9.40 mm) rib pitch — high-power industrial applications such as large conveyors and agriculture equipment
The Part Most People Miss
A PJ belt listing is not necessarily a complete belt.
The product photo might show what looks like one wide, multi-rib belt — but the price and quantity are often for a single rib. Belts are cut and sold to the exact rib count a user needs, so one unit of "610PJ" gets you one rib of that belt, not the full width.
How Many Ribs Do You Need?
Count the grooves on your pulley — that's your rib count. Or if you have an existing belt that’s broken count the number of ribs.
If your pulley has six grooves and you order one rib, you'll only receive enough material for one groove. You need a 6 rib belt.
Why Are PJ Belts Sold Per Rib?
PJ belts are widely used on:
· Roller conveyors
· Material handling equipment
· Packing machinery
· Light industrial power transmission drives
Because many of these applications only need a specific rib count, selling by the rib keeps belts cheaper and lets customers order exactly what fits their pulley — rather than paying for width they don't need.
Identifying Your Existing Belt
Belts are typically marked with rib count first, then the profile and length — for example:
6PJ610
This breaks down as:
· 6 ribs
· PJ profile
· 610 mm length
To replace it, order 6 ribs of 610PJ — not 1 rib of 610PJ.
Before You Order, Check:
· Belt length
· Belt section (PJ / J)
· Number of ribs required
· Whether the listing is priced per rib or as a complete belt
Getting these four details right the first time means the belt that arrives is the belt that fits — no surprises, no returns.
Browse our full range of Poly-V (PJ) Belts, or get in touch if you're not sure how many ribs your application needs.