The question we hear most is "Which length should I buy?" The answer lies in two numbers: how thick the bundle is (maximum bundle diameter) and how much force the tie has to hold (tensile strength). An easy rule of thumb: the first number decides the length, the second decides the width.
Length follows bundle diameter
The longer the tie, the larger the circumference it can wrap. The "maximum bundle diameter" in our catalog is the largest bundle that tie can close around. Gather the wires as they will be bundled and measure the diameter — or, if that is awkward, measure the circumference with a tape and divide by 3.14. Then choose a size whose maximum bundle diameter comfortably exceeds that value.
Avoid a size that only just reaches the maximum bundle diameter. You need enough tail past the head to grip by hand or with a tool and pull it tight, and a little spare length lets you add a wire or two later. Any extra tail can simply be cut off after tightening.
Width follows the load
A cable tie's strength comes mainly from its width and thickness. In the Allpum AP series, the 2.5 mm-wide AP100 is rated at 80 N (8 kgf), while the 9.0 mm-wide AP450, AP540 and AP780 are rated at 715 N (72 kgf). When the tie carries a real load — a heavy bundle, vibration, or wiring hung from a structure — choose a wider size. The rated tensile strength in the table is a limit not to be exceeded, so keep the actual load well below it.
| Item | Length (mm) | Width (mm) | Max. bundle Ø (mm) | Tensile (N/kgf) |
|---|---|---|---|---|
| AP100 | 100 | 2.5 | 22 | 80 / 8 |
| AP140 | 140 | 3.6 | 36 | 134 / 13 |
| AP200 | 200 | 4.8 | 50 | 220 / 22 |
| AP270 | 270 | 6.0 | 74 | 356 / 36 |
| AP300 | 300 | 4.8 | 80 | 220 / 22 |
| AP370 | 370 | 7.6 | 106 | 512 / 52 |
| AP450 | 450 | 9.0 | 129 | 715 / 72 |
| AP540 | 540 | 9.0 | 155 | 715 / 72 |
| AP780 | 780 | 9.0 | 230 | 715 / 72 |
Longer does not mean stronger
Two rows in the table deserve a closer look. AP300 is longer than AP270, but at 4.8 mm wide it is rated at 220 N — lower than AP270's 356 N. And AP450, AP540 and AP780 are all 9.0 mm wide with the same 715 N rating; only the bundle diameter they can wrap changes with length. When you pick a long tie for a thick bundle, check the tensile strength too.
Step by step
- ① Measure the diameter Measure the bundle diameter (or circumference ÷ 3.14).
- ② Shortlist by length Shortlist sizes whose maximum bundle diameter is comfortably larger.
- ③ Check the load Consider bundle weight, vibration and whether the wiring hangs from the tie, then pick a width with enough tensile strength.
- ④ Check the environment The AP series operating range is -40 °C to 85 °C. For long sun exposure choose the UV-resistant black ties; for higher temperatures or flame-retardant needs, look at our flame-retardant and heat-resistant ties.
Common mistakes
- Daisy-chaining short ties The joints become weak points. Use a tie that is long enough to begin with.
- Choosing by length alone As AP300 shows, a long but narrow tie holds less force.
- Loading to the rated limit The table value is a limit. Keep the real load well below it.
- Overtightening thin cables It can crush or damage the insulation. Tighten only enough to stop the bundle moving.
Packing units (bulk and retail) and colors for each size are on the product page. The same AP specification is made at our Gwangju headquarters plant and by our Thai subsidiary — the specifications are identical; only certification and country of origin differ.
