Marklin 2210 - Curved K-Track R0, 45 degrees tight radius
Length 1/1 = 11-5/8". 45 degrees. Small radius for branch lines and industrial trackage.
Cannot be used for long locomotives and cars.
This is an extra tight curve, so you can plan railservice to industrial areas etc.
Sold and priced by the piece, 10 pcs in a box.