Attention: The important instructions about training dogs accept the dog head collarStep 1 Put the collar where the dog can touch it, let the dog sniff it, continual praise and treat, repeat until your dog indicates that the collar looks interesting in a way.Step 2 Take the collar and gently touch it to your dog's body, slowly approaching the dog face. Give a treat. Repeat until your dog feels well.Step 3 Holding the collar in one hand and giving a treat in the other hand, so he needs to put his nose inside the collar to get the treat. Repeat this steps until your dog seems used to the collar.Step 4 Put the collar on the dog and quickly lock the buckle. Treat. Removing the collar after several seconds.Step 5 Repeat step 4 few times until they become used to wearing the collar, slowly lengthen the amount of time they are wearing it.Attention:Don't let your dog wear the collar in a long time. Notes on fasten dog leash Please fasten the dog leash to the strap of dog?s neck, rather than D-ring?mouth loop?. If you fasten the dog leash to the ring, the collar might be pulled off when dogs are running.Size Map: S - Snout Circumference: 5.11-10.62""; Neck Strap: 12.59-15.74"" M - Snout Circumference: 6.29-12.59""; Neck Strap: 14.96-18.11"" L - Snout Circumference: 7.08-14.56""; Neck Strap: 16.53-21.25"" XL - Snout Circumference: 8.66-16.53""; Neck Strap: 18.5-25.98""