This is Magigoo Pro Flex, the adhesive specifically designed for 3D printing in flexible plastics. It offers a strong adhesion platform for thermoplastic elastomer copolymer based filaments

Magigoo is an easy to use 3D printing adhesive designed to reduce warping in FDM/FFF 3D printers. Warping, among other factors, is caused by the differential cooling of a print during a 3D printing process.

For printing repeatedly and reliably remember to apply Magigoo Pro Flex on your print bed before printing in flexible filaments.