Why are there different sized Go playing grids?
(19x19, 13x13, 9x9)

Go can theoretically be played on a board of any size without changing the rules. Although the standard Go board size is 19x19, both 13x13 and 9x9 are accepted alternatives. The advantage of playing on a smaller board are that the game doesn't take as long to play. This is especially interesting for beginners, since shorter 9x9 (or 13x13) games allow a player to get a feel for Go more quickly.

Why aren't the spaces on the Go board square?

This is one of several interesting aspects in the design Go equipment, intended to offset the typical perspective of the Go player. The squares are slightly longer (23.7mm) than they are wide (22mm) in order to appear square from the perspective of the seated Go player.

Why are there black circles on several of the intersections?

Go offers a simple handicap (or rather an advantage) system which allows players of different skill to nevertheless play each other on a balanced field. At the beginning of the game black receives one or more extra stones which are placed on the circled intersections on the Go board. Depending on the game results, black can receive more or less advantage stones in future games.

Which different sorts of Go boards are available?

Material

• Low Cost - Go boards can be made of virtually any material, for example: card, wood veneer and MDF. The colour tone of the board should lie somewhere between black and white, in order that pattern in both colours are easily recognised.
• Wood - Go boards can be made of many differen types of wood, with emphasis being on regularity of colour and grain pattern and colour tone, which should be neither too light or too dark. Commonly used woods include maple, beech, pine and Japanese woods such as katsura. Tips on looking after your wooden Go Board

Style

• Board - Go boards are made in a standard size (424,2 x 454,5mm) but with variable thickness up to a maximum of 80mm (thicker boards are usually sold as Go tables).
• Portable Board - Go boards made in one single piece are visually appealing but not very portable. To solve this problem, Go boards are often also manufactured in two piece versions. The methods of joing the two halves varies: magnets and hinges are the most common methods.
• Table - Go tables are the most attractive and most expensive way to play Go. A Go table is made up of a thick (80 - 160mm) block of wood raised further by wooden legs. Players commonly sit on floor cushions in the Japanese style when playing on a Go table.