Bidders in these multi-unit procurement auctions sell one or more items, e.g. units or tons. Bidders are given random signals that can be either 1) known private costs, 2) unbiased estimates of a common cost 3) separate components of an unknown common cost. Bidding in each auction can take place in "rounds," with a cutoff that decreases (clock auctions). Single-round sealed-bid procedures are also available with either "receive as bid" (discriminatory) or uniform (market-clearing) prices. Other setup options include reserve prices, maximum bids, various information settings, and a chat room for collusive disucssions.