Until now, all Stanley-type bench plane irons were bedded at 45°, or common pitch. But the famous English Smoothers like Norris are usually 50° (York Pitch) or 55° (Middle Pitch). The higher pitches make smoothing difficult wood easier. Lie-Nielsen's unique High Angle Frogs quickly convert their No. 4 and No. 4 1/2 Smoother to York or Middle Pitch. These frogs will also fit our other Lie-Nielsen planes with 50mm(2") or 60mm(2.3/8") blades. Please note these will not fit other makes of planes.