Gender ultrasound at 13 weeks

So I went to this specialty ultrasound place with my son at 15 weeks and it was clear as day in the 2D, let alone 3D, that he was a he. I called to schedule for this baby and when I told the woman when I'd be 15 weeks she asked when I'd be 13 because I could come in that early! I guess their equipment is super new and detailed. I keep wondering though if I should move the appointment a week or so later. I'm so afraid it will be inconclusive or they'll say girl and it will be a boy! So who has seen a clear gender at 13 weeks, was it at your doctor or a specific gender US place? I'm so impatient!!