ADC Model 284 is used for walk along operation only and is supplied with no pulleys or operating cord. The difference between Model 284-N and 

284-R is as follows: Model 284 employs 2801 single and 2802 master carriers. Model 284-N: No. 2851 Nylon Ball-Bearing Single Carriers and No. 2852 Nylon Ball-Bearing Master Carriers are used for increased capacity. 

Model 284-R: No. 2849 Neoprene Ball-Bearing Single Carriers and No. 2850 Neoprene Ball-Bearing Master Carriers are used for increased capacity and extra quiet operation.