In the outer walls of our house are some holes in the clinker (missed out mortar). Probably for ventilation.
Some of these holes are regularly visited by bumblebees. Basically, this is not a problem - but near the terrace it is unwanted.
That's why I designed this thing. It fits on ventilation holes with the dimension of 10x60mm.
BTW: I will install the barriers at the earliest in September - from then on, no [living] bumblebees should fly around.
UPDATE 05.07.2018: added a less break-sensitive V2
I printed mine with PLA+.