Finally got a response to the email I sent them.
Thank you for reaching out, and we've got you covered with our Lifetime Guarantee! The socks you send in do not need to have holes.
To file a warranty claim with us, please follow this link:
Unconditional Lifetime Guarantee.
Once you complete the form, please print it out and mail it to us along with the clean sock(s) you submit for replacement.
Generally, customers get the best shipping rates with USPS. We strongly recommend keeping your tracking number until you receive your credit, just in case!
At this time, please allow up to 4 weeks for processing once we receive your claim.
Once we process your claim, we will email you a warranty credit code for the retail price plus free shipping. Use your replacement credit to shop for your new socks on our website!
Please don't hesitate to let us know if you have any additional questions or if there is anything else we can do to help you with your warranty claim.
Thank you for choosing Darn Tough.