Very glad you provided a picture link. If the center bar appears to pivot, does it do so? if yes, then i suspect these are antennas and being dual, provide a wide range for reception. if it pivots the round section acts as a base while the center portion is the antenna. The Asus support website may offer what was provided when you brought the PC, if you enter your S/N# or such to better help you. However, that's a guess. You may have to replace both in order to be similar an antenna dual set but still provide the same service. Just look for antennas, they will still connect to the same type connector from your wifi card, verify that. Replacement antenna will probably look more like typical antenna but still do the same job.
I suspect there is some model# on those devices, google for that or if you're lucky some part number from some decal or sticker.
I have an asus desktop and these two wireless parts are asus parts that are connected to my wireless card to allow connection from a router. I need to replace one and dont know what they are called or where to buy them. Any help?