Type 1) A-grain, also known as a Tangent cut. This cut of balsa has a long grain, smooth creamy appearance and is very flexible but lacks stiffness. This cut is called a tangent cut because the sheets of balsa are sliced off at tangents to the growth rings.

Ideal for: sheet covering on curved fuselages. Wing leading edges (D-boxing etc), forming tubes (electric motor holders) and flexible spars.

Type 2) C-grain, also known as a Quarter grain. This cut of balsa has shorter grains, typically mottled in appearance, it is quite stiff but subsequently brittle and prone to splitting along the length of the sheet. The sheets of balsa are cut at a perpendicular angle to the growth rings. Of all the cuts this is regarded as the most aesthetic.

Ideal for: Sheet balsa wings and tails, flat fuselage sides, wing ribs, fuselage formers, and wing trailing edges.

Type 3) B-grain, also know as Random or Mixed grain cut. These sheets vary a lot in properties; often a single sheet will vary from A to C grain across its width. If possible, avoid buying sheets that change grain type across the surface, i.e. they appear to be C grain on one side and A on the other edge; these will cause warping issues. You will find that most local hobby shop stock tends to be in the 'B-grain' category simply because from a given tree there is only going to be a limited number of quality A and C selections. This cut of wood is useful as a general-purpose selection. If you don't specifically have a Tangent or Quarter grain stock selection to use for the job at hand, then the random cut will suffice.

Density: Balsa, like all woods, can vary in density or 'mass per volume.' The denser a piece of balsa, the more it will weigh. The relationship between weight and strength is not always consistent so don't assume that heavier equals stronger.

Thickness: Balsa is supplied pre-cut into an array of thicknesses. Kits and plans will nearly always specify what thickness to use (and sometimes what grain). Common thicknesses are 0.8mm (1/32"), 1.5mm (1/16"), 2.4mm (3/32"), 3.2mm (1/8"), 4.8mm (3/16"), 6.4mm (1/4") and 12mm (1/2"). Because both imperial and metric thicknesses are used depending on where the balsa is cut, you may find some thicknesses unavailable. There is no problem if the plan calls for 3/16" and you can only obtain 5mm, these are small differences and will usually be sanded off later.

Length: Typically balsa is sold in 914mm (36") and 1000mm (40") lengths. Longer sheets can be obtained on special request from the cutting factory.

Width: The two most common widths are 75mm (3") and 100mm (4"). The wider the sheet the more expensive the balsa becomes, this is because a wider sheet requires a larger tree to be cut reliably.