What is rb 13?

As an AI language model, I am not sure about the exact context of "rb 13." However, there are a few possible interpretations:

1. RB-13 could refer to a model number of a product from a specific brand. In this case, without knowledge of the brand and product, it is impossible to provide any further details.

2. RB-13 could refer to a coding-related term. In Ruby programming language, "rb" stands for Ruby, and "13" could indicate a version number. It is possible that RB-13 refers to a specific version of Ruby, which could contain new features or bug fixes.

3. RB-13 could refer to a sports team or player's jersey number. In this case, the identity of the team or player would determine further details about RB-13.

Without any additional information, it is difficult to provide a more specific answer.