Here's a breakdown of the likely meaning:

Choke Chain: This is a type of dog training collar made of metal links. It is designed to tighten around a dog's neck when they pull on the leash, providing a quick correction. When used correctly with a "pop and release" technique, it is intended to discourage pulling and other unwanted behaviors. However, it can cause injury if used improperly.

P135: This is likely a specific product or model number used by a particular retailer or manufacturer. It doesn't appear to be a standardized size or specification across the industry. The number "135" might relate to the chain's length, the diameter of the links, or simply be a unique identifier for that product within a company's catalog.