The large cache is typically larger than about 10 litres in size. They are typcially placed to cater for large swaps, an example being No Small Swaps in the Forest. They may include 20 litre drums, old wine barrels or even old fridges. Of course anything this large takes a bit 'hiding' so there are 2 methods used. Firstly it can be well hidden in far away and muggle free places. Secondly the hider can just face the music that it's bloody big and make it look like something else. This may include easy to recognise objects like letterboxs through to fake electrical/communication boxes complete with fake antenas.