details about product: Semi-Cutaway Collar Non-Iron Stretch Print Diamond Shirt - Light Blue

Thank you for taking the time to share your feedback regarding the sizing of the Large shirt you ordered. We're truly sorry to hear that it didn't meet your expectations. Our large size would be suitable for a chest up to 45" so as you had mentioned you are a 40" chest we would recommend the medium size which would suit a chest up to 41.5" as shown in our sizing guide here: https://www.charlestyrwhitt.com/uk/sizing-guides (please scroll down to casual shirt sizes). As you had ordered a casual shirt it would be in "alpha (casual) sizing" rather than collar size 16" for example. Our formal and business-casual shirts will have collar and sleeve sizes stated. Please also check our guide which will explain how our fits work: https://www.charlestyrwhitt.com/uk/editorial-style-tips/about-our-shirt-fits.html Size and fit will inevitably vary from brand to brand so we would always recommend taking body measurements and referring to our guides before making a purchase. We are also here to help with this if needed of course. We also have a hassle free return process with free exchange over at https://ctshirts.intelligentreturns.net/ so feel free to use this at anytime within your six month guarantee window. We appreciate you getting in touch and we hope to see you shopping with us again soon.