What's In Your Core? You've put the time and sweat into your training, now it's time to step up your game. The Core Series gi is made for players that are ready for competition. In a nutshell, Core series BJJ gi fabric is thicker [than Essential’s] and harder to grab by your opponents Trusted by Professionals. From pro athletes like IBJJF Champion Guilherme "Bomba" Vasconcelos, UFC fighter and world class Jiu Jitsu player, Gilbert Burns, to legendary coaches like John Danaher. Sanabul is a brand you will find on elite athletes Competition Ready. There's nothing worse than getting stopped at the uniform checkout station. Core Series Jiu Jitsu gi will pass all the measurements of IBJJF rules (White, Blue and Black). Please note the Grey variation is not IBJJF competition approved. Please refer to the IBJJF rule book for specifics