When it comes to sealing the gap between your truck cab and camper shell or sleeper, getting the correct size accordion boot is critical. Especially if it is too short. If you do not get enough material you will end up with a gap. That gap will not properly seal the opening. Therefore getting the proper measurements is easy—and once you’ve have the numbers, selecting the correct boot is even easier.
This guide will walk you step by step the process that will help you find the perfect fit for your vehicle setup.
What You’ll Need
- A tape measure
- A friend (optional, but helpful)
- A notepad or smartphone to record measurements
Measure the Gap Between the Cab and Camper
Park your vehicle on level ground with the camper shell installed (or at least positioned). Then:
- Measure the distance from the back of the truck cab to the front of the camper shell.
- Take this measurement at the window opening—not the edge of the roof or bed.
- Measure in three places: top, middle, and bottom. Gaps aren’t always uniform.
- Record the largest measurement in inches.
When the boot is installed on the vehicle you don’t want the boot to be fully expanded. Due to movement it is important that the boot have some slack to allow for movement.
Boot Size by Gap Range
| Gap Size (inches) | Recommended Boot Size | Notes |
|---|---|---|
| 2″ –4″ | Standard Accordion Boot | Part number 541 |
| 3″ – 7″ | Extra Wide Accordion Boot | Part number 543 |
| 4″ –10″ | Ultra Accordion Boot | Part number 544 |
| 5″ – 15″ | Boot 15 | Part number 546 |
What If You Have Sliding Windows?
If your truck cab and/or camper shell has a sliding window, a standard accordion boot will not work properly unless the slider is removed. That is because there is no thin wall or flange to attach the boot. This thin wall should be +/- 1/8″. The thin wall could be fiberglass, sheet metal.
Important: If the sliding window remains in place, an alternative is to use the compression-style boot instead of an accordion boot.
Here are your options:
Option 2: Use a Compression Boot
If you prefer to keep the sliding window intact, a compression boot is a better solution. These are designed to compress between the cab and shell without requiring a flange or thin wall to attach the boot.
Click here for information on Compression Boots.
Option 1: Remove the Sliding Window
Removing the glass allows the accordion boot to seal directly to the frame, creating a proper pass-through. Please note each truck is different. It is best to do some research to make sure that there is an adequate flange.
Measure the Window Opening
Along with measuring the gap between your truck cab and camper shell, you’ll also need to measure the window opening perimeter—this is the area around the edge of the window where the accordion boot will attach.
Important: The window openings on both the truck cab and the camper shell must be the exact same size for the accordion boot to fit and seal properly.
Two Ways to Measure the Window Opening:
Option 1: Flexible Tape Method
Use a flexible tape measure and run it around the full outer edge of the window frame to get the total perimeter.
Option 2: Width + Height
If you don’t have a flexible tape, use this formula:
- Measure the widest part of the window opening (width)
- Measure the tallest part (height)
- Multiply each by 2 (width × 2 + height × 2)
- Add those together to get the total perimeter
- Convert the result to feet
Example: A window 36″ wide and 24″ high
36 × 2 = 72
24 × 2 = 48
72 + 48 = 120 inches = 10 feet
For your convenience, you can use our Boot Opening Measurement Calculator to input your dimensions and find the right boot size instantly.
Mounting Tips
- The accordion boot has an embedded Metal Spring Clip that runs the length of the boot. There is a groove in the material that slides over your window flange for a pressure fit.
Ready to Order?
Once you’ve got your measurement, head over to our shop and select the correct size:
If you’re still unsure, feel free to contact us with your truck model, shell brand, and gap measurement—we’ll help you pick the perfect fit.
Pro Tip: Don’t Trust Generic Gaskets
Foam or brush-style gaskets break down fast, let in water, and don’t support a usable pass-through. Accordion boots are made of durable EPDM rubber with an embedded metal spring clip —built to last and actually work.