These 50 mm / 2 inch omni wheels feature multiple durometers:

• 35A: Softer rollers for high traction
• 50A: Middle ground between grip and wear
• 80A: Harder rollers for long life

They also have a standard 14 mm Hex Bore, letting you choose between 4 different bores:

• 0.375 in. Hex – includes 14 mm Hex to 3/8 in. Hex Adapter (am-3905)
• 0.5 in. Hex – includes 14 mm Hex to 1/2 in. Hex Adapter (am-3904)
• 5 mm Hex – includes 14 mm Hex to 5 mm Hex Adapter (am-3909)
  
• 14 mm Hex – no adapters included

Stack several of these wheels on a shaft to craft an unstoppable intake system for your robot that can be used to center game pieces.