Very pleased with this after my initial disappointment with an under-size CASE LOGIC SKU-PHDC-1. I have a Silicon Armor A70, which is a larger-than-average portable hard drive, and it fits snugly and flush in either side of the case (behind the restraining band or behind the net pocket). In fact, I reckon it'd hold two such drives. The case is not perfectly square, but I measured the practical external dimensions as 170 x 115 x 40 mm and internal as 145 x 94 mm. I can't measure the internal depth with the case closed, but clearly it's the external 40mm less the thickness of the case wall, so it'll accomodate a pretty thick drive. Well made, solid construction.