The RB wagon was introduced in 1930 with 177 being constructed up until 1937. These wagons where later converted to RBWs for bulk wheat traffic with the addition of hungry boards. The RB wagon model is in Sn3½ and was developed by Marbelup Models and comes as a 3D printed body supplied with kadee couplers. The kit does not include bogies, wire or screws.
Assembly tips can be found here: Assembly Tips from Marbelup Models