The product is untreated and can be cut, sanded, stained, painted etc. They are excellent for a wide range of uses and are suitable for use with food.
Please note that the length can vary by the odd millimetre either way and the shorter dowels (15,20,30cm) often come up a millimetre or so short. Birch wood is a natural material and may have some marks and blemishes, the colour can vary and the odd dowel may have minor signs of warp but can normally be teased back straight.
The smaller dowels are machine cut in house and the ends may have some very minor roughness or nicks and sanding may be advisable but is not normally required.
The size(diameter) of each dowel is the maximum size and can be very slightly smaller as a result of the manufacturing tolerance.