An adjustable liner, for immersion in the cooking oil of a deep fryer, includes: (a) two partial baskets, each having a bottom surface with four edges and three side surfaces, each of which extends upwardly from one of the bottom surface's edges so that the fourth edges of these partial baskets are free edges, (b) wherein the bottom surfaces of each of these partial baskets has a porosity chosen so as to allow the cooking oil to circulate through these bottom surfaces when the deep fryer is in use, and (c) wherein the lengths of these partial baskets' free edges are such as to allow one of these partial baskets to fit and nest within the other so as to yield a liner having adjustable length that can be custom fitted to the width of the deep fryer in which this liner is to be retrofitted for use.