Boy's SFI-Rated Racing Jacket Size 10 Question: I am looking for a racing jacket for my son. It needs to be fire retardant. I'm looking at the K1 Triumph jacket. Woudl that be appropriate? He wears approx a size 10 boys. What size would that be in your chart? You are absolutely certain it is fire retardant, right? Answer: The K1 - Triumph Jacket would be a great choice for a kid's fire retardant jacket. A size 10 in boys would be equivalent to a 5X-Small in this jacket. We have this size in stock. It's an SFI-Rated jacket meaning it passes the SFI Foundation's standards for fire retardancy.When you get to the track they will require you to show the SFI-Rated tag on the jacket to prove that it is fire retardant. On this jacket this appears on the left arm: /images/K1/triumph_jacket_1_full.jpg Let me know if you have any other questions!