This is the perfect sight for your 2240XL and Crosman Custom Shop KT series airguns.
LPA Mim Rear Sight for the Crosman Steel Breech:
Fully adjustable for windage and elevation.
Fits dovetail notch and ideal for Crosman’s steel breeches.
Does not fit 3/8″, 11mm, Weaver or Picatinny dovetails/bases