The bracket off Gia Cuong Thinh's K Series has 5.5 mm thickness steel and Zinc plate to prevent rust and corrosion. The PU is mold on Steel core is quite sturdy, good wear and tear resistant. Do note that this one has Steel hubs: small but very effective in dealing with dust intrusion.
Pneumatic tire absorbs chock on uneven floor by cushion of compressed air. Absolutely recommended for hospital, resort, hospital, labs, outdoor, etc. However, price is steep: 2 - 3 times higher than the domestic solid rubber one.