Finned X-WingA Finned X-Wing occurs when there is a X-Wing with additional candidates.
In the sudoku diagram below, either in the R4C3 or R5C3 cells (marked in yellow) you can place the digit 6 or you have the X-Wing pattern, i.e. in the third and sixth columns the digit 6 can only be placed in the cells of the sixth and ninth rows (candidates marked in blue). Thus, we can remove the digit 6 from the remaining cells of these rows, which simultaneously see the cells R4C3 and R5C3, and therefore from the cell R6C2. After applying this method in the sixth row, the digit 4 can only be placed in the R6C6 cell.
In the sudoku diagram below there is one additional candidate (R2C4 cell marked in yellow), which "spoils" the X-Wing pattern for the digit 5. So either the digit 5 can be placed in the R2C4 cell, or there is a X-Wing, i.e. in the second and sixth rows the digit 5 can be placed only in the first and fifth column cells. So the digit 5 can be eliminated from the R1C5 cell. After this elimination, only the digit 4 can be placed in the R1C5 cell.