When sourcing Double Happiness (DHS) equipment, particularly rackets and rubbers, buyers must look for the ITTF (International Table Tennis Federation) certification logo. Professional rubbers like the Hurricane 3 or Skyline series are categorized by sponge hardness (e.g., 39, 40, 41 degrees) and thickness. For wholesale purposes, ensure the products are labeled as 'Provincial' or 'National' grade if targeting high-end athletes, as these undergo stricter quality control for tackiness and elasticity compared to commercial versions.