Isosport 1600 base, check for protective film.
Clear base, (~70% transparency ) 0.4mm thick, for wakeboards and kiteboards. Very comfomable, affordable and good choice for bottom or top.
The material is grinded and flame treated on the bonding side. The outside has a S5 STRUCTURE (meaning not glossy but structured). You can easily find the grinded side by checking the fine hairs. If you grind a base you always get some fine hairs on the top side but if you apply a structure like S5 you cannot find any fine hairs on the surface.
So grinded and flamed side (with fine hairs) is bonding side and S5 is outside.
Some manufacturers call this ptex sintered base for ski and snowboard.
PS: Please before using check if your topsheet has protective film on the outside. We try as ofen as we can to get topsheet with protective film but some batches do not have it. In this case you can tape the topside of your topsheet with clear application tape (ebay) or contact paper for protection of needed.