Wood Metal Graphite Oversized Metal with Composite Face Wood There are basically two types of wood used, persimmon and maple. Solid heads are usually persimmon. Laminated ("plywood") heads are usually maple. Persimmon heads are made by using a sophisticated turning machine. The process is much like making a duplicate key for a lock. The second, and most commonly used, wood is laminated maple. Generally, 1/16-inch veneers of maple are laminated together much like a sheet of plywood. Then the veneers are heated and pressurized, and finally turned like the persimmon heads. While many golfers indicate that they have a more solid feel at impact with persimmon heads, studies show no support of this. Other golfers prefer the laminated maple, reasoning that they last longer. Metal Investment cast metal heads have gained popularity, mainly because of the added control of peripheral weighting (which was not a true design goal, but a product of the casting process to achieve proper weight). The stainless steel heads are cast hollow to restrict excessive weight, and usually filled with polyurethane to muffle impact noise. Metal "wood" heads have also been noted as adding distance to center and off-center shots. Graphite The same material that is used for shafts is also used to make graphite heads. There are two subtle variances in manufacturing techniques. In one case, the graphite prepreg is mixed with an ABS plastic, and is injection molded into a head. In the second version the prepreg is given an epoxy base and the mixture is compression molded. Graphite heads are manufactured with the same weight as the wood and metal heads, but are generally much larger than conventional heads. This increases the size of the "Sweet spot". No tests yet have proven graphite heads to be more forgiving or longer than other materials. Oversized The general consensus is that "oversized" heads, generally made of stainless steel or graphite, create a larger "sweet spot". This produces a longer and straighter flight trajectory on off-center hits. When using stainless steel, the walls of the head must be made thinner to keep the overall weight "normal" (191-205 grams for a 1 wood). This has caused some metal "wood" faces to "crush" or dent. For this reason, some manufacturers are bringing "Mid-sized" metal woods to market, which allows the "sweet spot" to stay large, yet keeps the walls of the head thick to prevent denting. Metal with Composite Face In conjunction with "oversized" clubheads, manufacturers are starting to use "face inserts" (normally plastic, graphite or lightweight metals). This allows them to produced the larger sized heads without worrying about the face crushing or denting. This also allows them to keep the overall weight of the head down. Face inserts, in metal "woods", is a fairly new design, and tests regarding their playability and forgiveness have not been published.