I bought the 24 colour Koi Field Box as an early Christmas present a few years ago as an impulse eBay buy, but I have to say I was quite impressed with the little set. Even though they are student grade colours, they are bright and clean and provide a lot of freedom for mixing beautiful, strong colours.
Thanks to the inclusion of the waterbrush (a brush with a tube handle you can fill with water, which can be squeezed down through the bristles as needed), you don’t need to carry heavy containers of water or unwieldy sets of long-handled brushes. The mixing palette lifts out and can be attached to either side or to the front of the box, making it suitable for both left- and right-handed people. The brush compartment is also big enough to hold a pencil stub and small eraser for those who like to sketch outlines before painting.
Here is a colour chart I did for the Sakura Koi set in my Moleskine watercolour journal.
As the colours are set into a plastic insert, the ‘pans’ cannot be replaced. However, once you’ve used up all the colours, you could either refill the little compartments with tube paints of your choice or simply remove the plastic insert entirely and put in your own selection of pans or half pans.
The 24-colour set isn’t really pocket-sized, but it does easily fit inside a backpack or handbag, ready to go whenever you have a quick sketching break at work or uni etc. You can also get an 18-colour set or a 12-colour set (the latter of which really is pocket-sized), but I was happy to trade the smaller size for a wider range of colours. It’s a good idea to keep an A5 sketch book handy along with the Koi set; the one drawback of the waterbrush is that it can be tedious to fill large areas with the relatively small brush, so unless you bring along extra brushes, painting bigger could be troublesome.
This would be a great gift for a young or beginner artist (the colours are non-toxic with no harmful pigments like cobalts or cadmiums) or a seasoned artist who just wants something to play with out in the field.
Here is a small picture I painted of a rainbow lorikeet in the Sakura Koi Water Colours (the green on the real picture isn’t this dark; my scanner is a bit rubbish):
It should be noted that these are marketed as student grade paints (though they are in the top range of student grade, in my opinion) and so far I have not been able to find mention of their lightfast ratings. Therefore it would be best to avoid displaying anything painted with the Koi set in areas of sunlight for long periods of time.
EDIT (26 May, 2016): It seems that Sakura have now released a 30-colour version of this watercolour box, as I found out when someone posted a picture of theirs on an art forum.