I used the large belt in the Sydney marathon, secured it further using the pulley elastic straps so it was snug and didn’t feel it shaking at all - wore it around my waist over my t-shirt. I’d tried on a competitors (3x the price!) 80cm belt, which was a little tight so would have had to go larger, but the elastic straps in the PURE belt are great. Waterproof phone pocket a great addition. I carried phone, 8 pure gels and an empty soft bottle with carb powder.