CPE Transparant is one of the new colors in the new material type of Ultimaker. CPE is a type of filament that is perfectly suited for complex, technical prints. CPE is a fairly stiff, strong and impact resistant type of filament.
CPE is also perfectly suited to bridge large gaps. CPE also needs to be printed on higher temperatures (between 230°C and 250°C) to get good results. This is also why Ultimaker adds an extra PTFE Coupler to each spool of CPE.