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Correcting the Airfix Anti-Pesto van wall (Part No. 34) in the forward position creates a gap between the wall and the raised floor in the back (Pt no. 50). This is a extension for part no. 50 to close that 11mm gap. Grooves in the top should line up witht the original kit part.
A complete floor replacement will be available as a Variant in the near future.