We often call the 4G boots the "Semi-Custom" boots. They are very similar to custom boots but without the price that often goes with it.
After all the experience gained by Groothuis by making custom shoes, they have now developed a standard ice skate boot. The shoes are manufactured in the same way like their custom boots. The speed skate boots are entirely thermoplastic and perfect mold able to your feet. The GB17 boot is a very high quality and comfortable boot.
The 17 is only available in black with a red zipper.
The boot is made of a microfiber inside. The shell is made of fiberglass and on the outside 2 layers of carbon. This boot has a thermoplastic shell built into the construction for easy heat molding. The outside of the boot is made of artificial leather.
The GB19 is made with same good quality materials of the GB17 but with real leather.