Xray have released a new 1.6mm thick top deck for the T4 chassis to increase traction and in-corner steering. With the thinner top deck, the car will flex more, which generates overall more traction. The top deck is a direct replacement for the standard 2mm top deck and is suitable for both carpet and asphalt surfaces.
#301196 Xray T4 Graphite Upper Deck 1.6mm
Source: Xray