What the class actually describes
ISO carriage classes standardise the vertical distance between the upper and lower fork bars and the height of the carriage plate. Because that geometry is standard, an attachment or fork set built for a given class fits any truck of that class regardless of who made it — which is exactly why an aftermarket attachment industry exists.
Classes step up with truck capacity. Class II covers the light and mid-range counterbalance trucks that make up most warehouse fleets; Class III covers heavier counterbalance machines; Class IV and above cover the large-capacity trucks used in ports, mills and heavy industry. The bigger the class, the taller the carriage and the further apart the bars.
How to identify yours
- Look for the class stamped or plated on the carriage itself — many manufacturers mark it.
- Otherwise measure the vertical distance between the top face of the lower fork bar and the top face of the upper bar.
- Photograph the carriage square-on, with the forks in place, and include the truck nameplate in a second photograph.
- If the truck already carries an attachment or a fork set, its markings will usually name the class.
Why it matters more than the truck brand
Buyers often ask whether an attachment fits Toyota, Linde or Hyster machines specifically. The honest answer is that the brand is almost irrelevant — the carriage class is what matters. A Class III attachment fits a Class III carriage whether the truck is a Toyota, a Linde, a Hyster, a TCM, a Jungheinrich, a Manitou, a Yale or a Feeler.
What does vary by truck is everything around the carriage: mast type, free lift, hydraulic services and the capacity available once an attachment is fitted. That is why a quote needs the make, model and capacity as well as the class.
When the class is not the whole answer
Some attachments are built to a specific mast and capacity rather than to a carriage — large tyre manipulators and integrated rotating carriages, for example, replace more of the truck’s front end than a simple hook-on unit does. Occasionally a truck carries a non-standard or manufacturer-specific carriage, in which case an adapter plate or a purpose-built mount is the route.