The letters PH, PJ, PK, PL, and PM in ribbed V-belts, also known as poly-v or multi-rib belts, indicate different belt profiles or sizes. Each of these letters designates a specific pitch (distance from one rib center to the next) and rib height. Here’s a simple breakdown:

• PH: This profile has a pitch of 1.6 mm and a rib height of 1.3 mm. It’s typically used in very compact drives and low-power domestic appliances.

• PJ: The PJ profile has a pitch of 2.34 mm and a rib height of 1.9 mm. It’s commonly used in home appliances and light-duty drives in industrial applications.

• PK: The PK profile, with a pitch of 3.56 mm and a rib height of 3.0 mm, is widely used in automotive applications for serpentine drives, where a single belt powers multiple accessories.

• PL: The PL profile has a pitch of 4.70 mm and a rib height of 3.5 mm. It’s typically used for high-speed, high-torque drives in industrial applications.

• PM: The PM profile, with a pitch of 9.40 mm and a rib height of 6.0 mm, is designed for high-performance drives in industrial applications, including heavy-duty machinery and agricultural equipment.

It’s important to note that these dimensions can vary slightly depending on the manufacturer’s specifications.