On the top page, you can check the list of products with a fixed price in the same row as each auction.
Items with an instant auction price will be marked with an icon. Bidding will proceed for items with an instant bid price as for regular items, but the auction will be closed when the bidding reaches or exceeds the instant bid price. The item will be marked "SOLD OUT" and no further bids will be accepted except from the member who won the auction.