Which chassis size carries which box: 4, 6, 8 or 12 twist locks against 1×40 ft or 2×20 ft. Frame lengths, lock spacing and what to tell us before we quote.
Lock count and frame length are two decisions, not one. The frame carries the box; the locks decide which boxes it can carry.
| Twist locks | Boxes carried |
|---|---|
| 4 | 1 × 40 ft |
| 6 | 1 × 40 ft |
| 8 | 1 × 40 ft or 2 × 20 ft |
| 12 | 1 × 40 ft or 2 × 20 ft |
Twelve locks does not mean twelve boxes — it means twelve positions, so one frame covers several box plans. The extra positions cost weight you carry empty on every trip, so they earn their place only if your traffic actually varies.
A frame built around a single 20 ft box is the shortest and lightest chassis in the range. It suits operators whose traffic is genuinely all short boxes — heavy commodities where a 20 ft box reaches its weight limit long before its volume limit, and short-haul terminal work where manoeuvrability matters more than capacity.
The catch is that it cannot take a 40 ft box at all. If a 40 ft box appears in your traffic even occasionally, a longer frame with the right lock positions will serve you better than two vehicles.
A 40 ft frame with eight or twelve lock positions is the general-purpose answer, because it takes one 40 ft box or two 20 ft boxes on the same vehicle.
That flexibility is the reason it is the most common configuration we build. It costs a little weight against a dedicated 20 ft frame, and it earns that back the first time a mixed load would otherwise have needed a second trailer.
Frame length, beam profile, lock positions and suspension are specified together rather than picked from a list, because the combination has to suit your box plan and your tractor. Tell us the boxes you actually run, in what proportions, and the fifth-wheel height of your tractor, and we will come back with a configuration rather than a catalogue page.
