The best luggage wheels are in-line skate wheels made of polyurethane (kind of high resilient flexible plastic). The wheels inside shall with a bearings ,such as with material Chrome steel Gcr15 ,or if you need with anti-rust function ,you can choose material with stainless steel ,These are the most hardwearing and durable wheels on the market today. Other materials used in suitcase wheels include rubber and other plastic.

MKL BEARING can produce bearings for Luggage Suitcase Wheels  ,such as 608 extended bearings ,and we also can produce customized extended bearings at customer's requirements .

Below here is R6 Non-Standard Bearings we can produce for rolling cases wheels .

And with 2 wheels are stronger for checked bags filled to the weight capacity, and are a tiny bit easier to manipulate over curbs and rough terrain because they're tilted back like a furniture dolly.