If there is a need we insert a layer of PEHD inside our bags. Especially if you want to integrate a bicycle battery or want to connect your SLOTBAG framebag with your frame using screws. The layer of highly durable polycarbonate will then be placed between two inner layers of fabric and is not visible neither from the outside nor the inside. But sometimes you need more. Like one of our customers who inserted a sheet of 1mm aluminium inside his SLOTBAG. He then connected the framebag with his frame using the bottle cage screw holes. This should be the nearest thing to a bicycle safe we’ve seen. Thanks again for the pics!