This is the little water color set that I travel with. Of course mine is a little more used looking, but I wanted to show the colors. The palette is not shown here, but slots into those four holes so you can place it on either side, or on top/bottom. The lid can be used to rest a postcard sized watercolor pad. Underneath is a thumb loop so you can balance it on one hand while painting with the other. Handy if theres nowhere to sit.
I haven't tried them yet, but I found some wonderful sets of these brushes on Amazon with different tips. The generic name for them is tank brush or waterbrush. As with all things these used to be expensive, but now you can get a really good set of six for around $10. They are definitely on my wish list. One word of caution, they dont all come with that handy breakapart with stopper that Sakura has.
Sakura click here.
Derwent click here
Arteza click here and here.
I've been planning to refill some well used colors in my set, but Sakura doesn't make replacements. They point out that some customers fill the empty pan with Koi tube paint, allowing it to dry before packing, which they don't recommend. I did find someone on Pinterest that had replaced their Koi brickets with Cotman half pans (above), but on closer examination this box doesnt look like mine, so I can't confirm that it works.
Since I purchased my Koi set I've discovered that there are several sizes of field set available with more color choices. The sizes I have found on the internet are 12, 18, 24 (mine), 30, 36, 48. As some of the larger sets are new, they may be on introductory sale at your local art shop. In Canada you can purchase at Opus here
Here are some of the selections.