What is the diameter of the NEO Flex portafilter and tamper? I'm looking at custom accessories.

Both the Flow Control and the Bottomless 2-in-1 Portafilter that the NEO Flex ships with are a unique-to-us size, so accessories that are not purchased through us, such as tampers or distributors, must be custom/specifically made-for-Flair. 

For both portafilters, the basket diameter is 40mm. The tamper it arrives with is 39mm.

We'd recommend a 39mm diameter for any third-party tools to ensure a snug-but-not-too-tight fit.