We present Tracs, a dual-sided see-through display system with controllable transparency. Traditional displays are a constant visual and communication barrier, hindering fast and efficient collaboration of spatially close or facing coworkers. Transparent displays could potentially remove these barriers, but introduce new issues of personal privacy, screen content privacy and visual interference. We therefore propose a solution with controllable transparency to overcome these problems. Tracs consists of two see-through displays, with a transparency-control layer, a backlight layer and a polarization adjustment layer in-between. The trans-parencycontrol layer is built as a grid of individually addressable transparency-controlled patches, allowing users to control the transparency overall or just locally. Additionally, the locally switchable backlight layer improves the contrast of LCD screen content. Tracs allows users to switch between personal and collaborative work fast and easily and gives them full control of transparent regions on their display.