When sourcing trolley bags, the shell material determines both weight and impact resistance. For Hard Shells, prioritize 100% Polycarbonate (PC) for its flexibility and crack resistance, or Aluminum-Magnesium alloy for maximum security and premium branding. Avoid low-grade ABS unless targeting the budget market, as it is prone to whitening and cracking. For Soft Shells, ensure a minimum of 1680D Ballistic Nylon or high-density Polyester with water-resistant coating to prevent tearing and moisture penetration.