When it comes to selecting corrugated cardboard for Simplex packaging, there are a few factors to consider such as the weight of the product being packed, the level of protection required, and the printing or labeling needs. Typically, a single-wall corrugated board with a C-flute or B-flute is used for Simplex boxes. C-flute board is commonly used for lighter products, while B-flute board provides more strength and is used for heavier products. However, if you need more protection or if the product is heavy, you may consider using a double-wall corrugated board, which is more rigid and can provide better cushioning.

Whether or not you need cushioning for your boxes will depend on the type of product you are packaging, as well as the shipping and handling conditions that the package will be subjected to. If your product is fragile or susceptible to damage during transit, then it's recommended to use cushioning materials to protect it. Cushioning materials can help absorb shocks and vibrations during shipping, preventing your product from getting damaged. Common cushioning materials include bubble wrap, foam, packing peanuts, and air pillows. These materials can be used to line the inside of the box, wrap the product, or fill void spaces to prevent the product from moving around inside the box

The suitability of the Custom Simplex Tray boxes for packing heavy products will depend on the specific dimensions and board grade of the box, as well as the weight and size of the product you need to pack. Simplex boxes are generally suitable for packing a wide range of products, including heavy items, as long as the box is appropriately designed and constructed. However, if you are packing very heavy items, you may need to use a double-wall corrugated board or consider additional reinforcement to ensure the box can withstand the weight.