The road measures 29.88 miles long and would take a car obeying speed limits 42 minutes to travel its length.
The B4391 is a B Road and is located in the Zone 4 Highways Region.
This is a true long-distance route, journeying through numerous towns like Ffestiniog, Pant Llwyd, BALA, Rhosygwalia, Llandderfel, Llangynog, Penybontfawr, Llanrhaeadr Ym Mochnant, Brithdir, and LLANFYLLIN.
The road passes through several counties, including Gwynedd, Clwyd, and Powys.