This quiet assimilation into the landscape is part of what makes the site worth attention: one section of the original bank still stands to around 1.4 metres, faced in stone and earthen in construction, while the opposing stretch has been levelled almost entirely flat, surviving only as a gentle rise no more than 0.2 metres high. A shallow external fosse, the ditch that would once have reinforced the defensive or social boundary of the enclosure, remains faintly visible on the outside edge.

A rath is a type of ringfort, the most common field monument surviving in the Irish countryside, typically dating from the early medieval period between roughly the sixth and tenth centuries. They served as enclosed farmsteads, the home and working space of a single family or small household, and their earthen or stone banks defined both a practical boundary and a mark of social standing. The example at Cashel Beg measures approximately 28.6 metres north to south and 30.5 metres east to west, placing it within the typical size range for such enclosures. What distinguishes its present condition is the uneven survival: the southwestern to northwestern arc of bank has been incorporated directly into the modern field fence system, meaning that centuries of agricultural use have simultaneously preserved and eroded the structure, leaving one side relatively intact and the other worn almost to nothing.