1.nylon production : 2.Product size precision 3.durable and functional: 4.high-precision caster 5.running smoothly Specification :Model No. R625z bearing ... :carbon,chrome,stainless steel,iron,ect.2.Roller Material:POM,nylon,glass fiber,etc3.OEM and non-standard bearing&roller orders ... .4. sealing from:2RS ZZ ,Z ,RS,OPEN (metal or nylon)5.colour: natural color, grren, orange, blue, grey, milky white ...