When to send it
Fit is the question every clothing and footwear brand wrestles with, and the answers are in your customers' wardrobes, not your returns data. Send this survey three to five days after delivery. By then the item has been tried on, maybe worn once, and there's still time to exchange it, so a customer who finds the size wrong can act on it instead of quietly giving up.
It works best for a single item per link. If your email tool can add the product name to the link, as ?product=Wide%20leg%20jeans, the first question names it and your results can be sorted by item.
Why these questions
The opening question uses a five-step fit scale, from too small through just right to too big. Five steps catch the difference between a little snug and unwearable, which a yes or no would lose. Because it's a single choice, you can chart it per product from the CSV export and see whether an item runs small or large at a glance.
Anyone who doesn't say just right is asked where the fit is off: chest, waist, hips, shoulders, length, sleeves or somewhere else, with several answers allowed. Running small across the shoulders is a pattern problem; running long in the leg might only need a note on the product page.
The next question asks whether they used your size guide and whether it was accurate. Many customers skip size guides entirely and pick their usual size. If that's the most common answer, the guide may be hard to find or hard to trust. Anyone who used it and found it off is asked what was wrong, which tells you which measurements to recheck.
The last question asks what size they usually wear in other brands. It's optional and says why it's there. Over time, it shows where your sizing sits against the brands your customers already know, which is exactly the comparison shoppers make in their heads.
The coupon
A shared 10% code for the next order thanks customers for a quick, useful survey. A customer who has just worked out their size with you is in a good position to order again with confidence. Everyone who finishes sees the code, whatever they say about the fit.
What to do with the answers
Check the fit chart for each new product after its first twenty or thirty answers. When one item clearly leans small or large, add a line on its product page, such as runs small, consider sizing up. That simple note often does more than a new size chart. Collect the size guide complaints and fix the measurements behind them before your next drop.
For the reasons behind returns that have already happened, use the return and exchange reasons template. For a broader look at how a product holds up after a few weeks of wear, try product feedback after two weeks.