The Topeak is one in a range of quick fit trunk bags, designed for commuting, errands and touring, though you'd have be pretty small to fit everything into its 7ltr capacity - I couldn't even fit a shoe in there!
All of them work only with Topeak's beam racks (£30). As usual, quality and attention-to-detail is really good. There are two fold-out dog-ear panniers on either side, with reflective strips. The main cargo area opens up wide and is padded with an elasticated pocket. It's also expandable, with a carry handle, shoulder strap and a bungee cord on top. The back has a reflective strip and light tab. The Topeak Trunk Bag is sleek and compact when folded down but is rather limited in carrying capacity.