Rollerblade RB 110/PRO X LINER (1PR) Replacement Liners - SaleReplacement liners for RB 110 3WD and RB PRO X, can also be used in RB Cruiser. These liners seem to work well as replacements for most skates including aggressive, street and urban. RB Pro X liners are used as replacement liners for your Rollerblade RB inline skates. The liner features the higher lacing on the Pro X but can be used on any RB series skate model and comes in sizes 220 320(US 4 14).