<p><b>Size:L<p><b> <p>Please read instruction before applying collar to your pet.</p> <p>1.Insert your pet collar through the inner ring loops of the cloud collar.</p> <p>2.Inflate cloud collar via air valve (pinch&blow).Inflate until it feels full,but not hard.</p> <p>3.Fasten collar onto your pet and use strap on the cloud collar to close.</p> <p>4.Choose the larger one once the size of your pet is between two.</p> <p>5.Always monitor the post-surgery pet to ensure collar is working properly.</p> <p>Size:X-S Diameter:6.1"Thickness:2.7"Neck Circumference:up to 4"</p><p>Size:Small Diameter:7.5" Thickness:3.3" Neck Circumference:6"-9"</p><p>Size:Medium Diameter:9.4" Thickness:3.5" Neck Circumference:8"-12"</p><p>Size:Large Diameter:15.3" Thickness:5.5" Neck Circumference:12"-18"</p><p>Size:X-L Diameter:16.9" Thickness:5.9" Neck Circumference:18"and up</p>