What thickness lifting belt should I get: 10mm or 13mm?

For most lifters, 10mm is the sweet spot — supportive enough for heavy squats and deadlifts but easier to break in and brace against. Specialist powerlifting communities consistently recommend 13mm only for advanced lifters who are already comfortable cueing intra-abdominal pressure against a stiff belt, and several reviewers in the threads we read suggest borrowing a friend's 13mm before committing.