Hyperdouraku finds an available Maruzen Walther P99 Carbine Conversion Kit for review. As far as we know, this product has been discontinued, though production may have resumed. This carbine conversion kit will make you think it is the RONI Carbine Conversion Kit which is made CAA, and for airsoft by the CAA Airsoft Division.
Read more about the review here and below is a video overview:
