As there is no suspension on stunt scooters the wheels, axle bolts and bearings take it all. Bolts can bend, bearings fracture and wheels can lose their tyres.
Almost all bolts are an M8 bolt for the scooter axle. These are steel so they are strong but if they do take a pounding they will usually only bend where an alloy bolt would snap. Bolts are easily replaceable with a 5mm or 6mm allen key and are inexpensive at around £2 each. Just be careful to get the correct length.
Bearings for scooters are usually in a sealed casing. These are the same size that fit skateboard wheels and some roller skates. ABEC are the best known brand offering various levels based on friction within the bearing which allows for a faster or slower ride.