MLB bats are made from three species of hardwood: sugar maple, white ash, and yellow birch. Maple dominates today at roughly 75% of all bats used in professional games, with ash accounting for about 20% and birch filling in the remaining 5%. League rules require every bat to be a single piece of solid wood, with no laminated or experimental designs allowed unless a manufacturer gets special approval from the Rules Committee.
The Three Approved Woods
Sugar maple is the densest and stiffest of the three options. That stiffness translates to a harder hitting surface, which means less energy is absorbed by the bat on contact and more is transferred into the ball. Maple bats also resist flaking and splintering during normal use, which gives them a longer playing life compared to softer woods. The tradeoff is that when a maple bat does break, it tends to shatter into larger, more dangerous pieces rather than gradually wearing down.
White ash was the standard for most of baseball’s history. It’s lighter and more flexible, giving hitters a slight whip effect through the hitting zone. Players who prefer a bat with more “give” on contact still gravitate toward ash. The downside is that ash bats dry out over time, causing the surface grain to flake and splinter. That gradual wear shortens their usable life, and many players found themselves going through bats faster than they’d like.
Yellow birch sits between the two. It’s harder than ash but not quite as stiff as maple, and it has an unusual structural advantage: birch absorbs more energy perpendicular to the grain than most materials, which makes it more resistant to breaking on mishit balls. In durability testing, most yellow birch bats either didn’t break at all or failed only at impact speeds well above the thresholds that would snap other woods. Despite those properties, birch remains a niche choice, partly because maple’s dominance is so well established.
How Maple Took Over
For most of the 20th century, white ash was synonymous with baseball bats. That changed in 1997, when Canadian bat maker Sam Holman crafted the first professionally approved maple bat. His company, SAM BAT, built a model based on the classic M110 profile that Mickey Mantle and Roger Maris had made famous decades earlier. Barry Bonds began working with Holman to refine the design, and as Bonds put together one of the greatest offensive stretches in baseball history, other players took notice.
By the mid-2000s, maple had overtaken ash as the most popular wood in professional baseball. The appeal was straightforward: a harder, denser bat that didn’t flake with use and delivered a stiffer feel at contact. Once star players proved it worked at the highest level, the shift became self-reinforcing. Today, three out of every four MLB bats are maple.
Size and Construction Rules
MLB’s Official Baseball Rules specify that a bat can be no more than 2.61 inches in diameter at its thickest point and no longer than 42 inches. There is no minimum or maximum weight written into the rules, which is why you see such wide variation in bat profiles across the league. Some hitters prefer a 31-ounce bat for speed through the zone, while others swing closer to 34 ounces for mass behind contact. The only structural requirement is that the bat be one solid piece of wood.
The Ink Dot Test
Not every piece of maple or ash is fit for a professional bat. Wood grain that runs at an angle to the length of the bat creates a weak point where the bat is far more likely to shatter. To catch this, MLB requires every game-used bat to pass an ink dot test. A small drop of ink is applied to the bat’s surface, and as it bleeds into the wood fibers, it reveals the direction and straightness of the grain. The league allows a slope of grain between 0 and 3 degrees. Anything steeper than that, and the bat is rejected.
This testing became especially important after maple’s rise in popularity. Because maple shatters into large fragments rather than splintering gradually like ash, a bat with poor grain alignment poses a real safety risk to players and fans. The ink dot standard helps filter out the most structurally compromised pieces of wood before they reach the field.
Bone Rubbing: An Old-School Technique
Long before maple became dominant, players would rub their bats with a dried bone, a glass bottle, or another hard smooth object to compress the surface wood cells. This process, called boning, slightly hardens the outer layer of the bat. A harder surface deforms less on contact, which forces more of the deformation onto the baseball itself and can produce marginally better results. Boning also reduces surface splintering, which was especially useful in the ash era when bats would flake and fray over a season.
The practice has faded somewhat. Maple is already naturally harder than ash, so there’s less to gain from compressing its surface. Some players still bone their bats out of habit or superstition. The old belief held that because bone and hide are related, a boned bat would attract the cowhide covering of the baseball. It’s a ritual with roots deep enough in the game that it hasn’t disappeared entirely.
The Threat to Ash
White ash’s future in baseball faces a biological threat that has nothing to do with player preference. The emerald ash borer, a small invasive beetle originally from Asia, infests and kills all North American ash species, including the white ash used for bats. The pest has spread across dozens of states and has already devastated ash populations in many regions. Estimates put the nationwide economic loss from a complete die-off of ash trees between $20 billion and $60 billion.
For bat manufacturers who still source white ash, the shrinking supply of quality timber is a growing concern. The trees that produce the best bat wood need to grow in specific conditions, with straight grain and consistent density, and those trees are becoming harder to find. This supply pressure is another factor quietly pushing the remaining ash loyalists toward maple or birch.