The Jones S-125 was a tidily presented, two-seat low-wing monoplane largely constructed from wood and with fabric covering.
Aft, the cockpit seated two in tandem over the wing under a sliding, three-part, tunnel-type canopy.
Its elevators had rounded tips, cut-outs for rudder movement and an internally adjustable trim tab port side.
The fin had a blunted, cropped triangular profile and the rudder, which reached down to the keel, was largely straight-edged.
Forward-reaching trouser fairings from the wing underside came almost to the ground, showing less than half the wheels; these had brakes that were foot-operated from the edges of the rudder pedals, allowing independent or collective use of brakes and rudder on the ground.