Heavy duty- for experienced and professional dog owners No visual safety indicator. This heavy duty is solid all of the way through Purchaser should be familiar with our safety mission and guidelines Guaranteed for life. Take away after any damage and return for replacement. Please read guarantee instructions. Medium black "original" heavy duty Dimensions: 1.75 cross sec/5 inch diameter Even more durable. No visual safety indicator Suitable for dogs 30-70lbs Durability scale score: 90 Large black "maxx" heavy duty Dimensions: 2.19 inch cross sec/6.25 inch diameter Even more durable. No visual safety indicator Suitable for dogs 60-100lbs Durability scale score: 97 Extra large black "buster" heavy duty Dimensions: 2.5 inch cross sec/6.25 inch diameter Even more durable. No visual safety indicator Suitable for dogs 80-100lbs + Durability scale score: 99.