This is an open ITT for C3S “Demo Cases” and aims at demonstrating the full potential of the C3S infrastructure, including the diverse set of datasets in the CDS catalogue and the CDS toolbox. This ITT will facilitate the creation of indicators, tools and visualisations that do not necessarily have a sustainable business case, but are excellent communication tools and will show-case the CDS and, hence, increase uptake. ECMWF expects that individual bids in the range between 50 000 and 150 000 euros will be adequate to achieve the objectives of this call, depending on the scope of the proposed demo case. Nevertheless, ECMWF may consider bids outside of that range if duly justified by the bidder. This is a rolling Invitation to Tender, whereby bids will be evaluated on a quarterly basis, with closing dates every three months (14 September 2018, 14 December 2018, 14 March 2019, 14 June 2019), when bids submitted during the previous calendar quarter will be evaluated. Bidders will be informed about the outcome of the evaluation within six weeks following each closing date. Reminders on the evaluation dates will be posted on the C3S website (https://climate.copernicus.eu/) at regular points in time. THIS EOI EVENT IS FOR ROUND 3 OF THE ROLLING ITT.