Holetto mainly uses E1 solid-core plywood. This kind of board has been a popular eco-friendly choice in recent years. E1 boards are rated as ultra-low formaldehyde, while E0 boards contain zero formaldehyde.
For traditional furniture made with plywood, use of volatile glues and adhesives causes the formaldehyde content to be high. When that type of furniture is installed, you will have a very unpleasant smell in your house. The paint used contains a lot of solvents, so it's impossible to achieve zero formaldehyde. E1 multi-layer solid core plywood is a safe to use, ecological board. Once they leave the factory, the veneer and wooden board are pieces of the same whole. They do not require any glue to bond, so formaldehyde content is extremely, which helps to provide customers with the healthiest product possible.
Another advantage of this style of board is the continuity it provides. The color outside perfectly matches the interior. With traditional furniture, the inside must be made a matte white, in which they will add an extra 10-20% surcharge.
It's worth noting that ecological boards, or E1 boards, are divided into different types according to the core material. The best is multi-layer solid core plywood, followed by high density fiberboard, then particleboard. Holetto chooses the best,  multi-layer sold core plywood, which of course also makes the cost more expensive. For high-density fiberboard, it is the cheapest and most commonly used E1 board. It is relatively weak and easily bends/deforms. It also will expand very easily when exposed to water. The worst performer is the particleboard. It has a wide range of disadvantages, even worse than the other choices, and is the most commonly used board in IKEA furniture. However, because of its cheap price, it still finds its place in the market.
So, when choosing custom-made cabinetry or furniture, you must pay attention to the type of board used.