Whipstock is　called deflector　tool .

It is specialized tool for guiding mill tool from one side milling casing to form elliptical window.

There are type SMD cementing deflector ,type KMD packer anchored deflector

Type	O.D. (mm)	Chamfer length (mm)	Connection	(mm) I.D. Of suitable casing	Type	O.D. (mm)	Chamfer length (mm)	Connection	(mm) I.D. Of suitable casing
SMD114	114	300	NC31	124.3—127.3	YMD114	114	300	NC31	124.3—127.3
SMD139	139	300	NC38	144.2—153.7	YMD139	139	300	NC38	144.2—153.7
SMD152	152	300	NC38	154.8—166.1	YMD152	152	300	NC38	154.8—166.1
SMD203	203	300	6 5/8″REG	216.8—228.7	YMD203	203	300	6 5/8″REG	216.8—228.7
KMD114	114	300	NC31	124.3—127.3	FMD114	114	300	NC31	124.3—127.3
KMD139	139	300	NC38	144.2—153.7	FMD139	139	300	NC38	144.2—153.7
KMD152	152	300	NC38	124.3—127.3	FMD152	152	300	NC38	154.8—166.1
KMD203	203	300	6 5/8″REG	144.2—153.7	FMD203	203	300	6 5/8″REG	216.8—228.7