It's a bit difficult to recommend a size for a puppy based on breed alone, especially mixed breed pups however each of our collars and harnesses are adjustable to accommodate different neck circumferences and girths.
Many customers have found the following suggestions to be helpful when shopping for a puppy:
Small breeds (< 20lbs as adults) typically fit into our size Small at around 7 months old.
This size would carry them into their adult years, however, depending on the breed (such as Pugs who need extra room to accommodate their stockier neck), a Medium may be required later on.
Medium breeds (< 50lbs as adults) typically start in a Small, eventually graduating to a size Medium (or Large depending on the specific breed such as Bulldogs who need extra room to accommodate their stockier neck).
Large breeds (< 80lbs as adults) typically wear a Small at 8-weeks, graduating to a Large at approximately 5-months.
Giant breeds (< 140lbs as adults) typically buy their dog's first collar in a Medium, eventually graduating to a Large and if greater than 115lbs, may eventually require an XL.