You can use either Competition knobs or Super knobs on Happ Tulip, Supers, and Competition joysticks. The 4-Way Tulip base is a true 4-way joystick with a diamond shaped restrictor plate.
You can have a choice of knob style (and for competition knobs - the choice of red, blue, green, yellow, or black).
Note: Competition knobs on a Super or Tulip base require the Tulip actuator (white Tulip actuator not the black Super hourglass actuator).
As pictured:
CB/CK CB/SK TB/CK
SB/SK Sb/CK TB/SK
KEY:
CB = Competition Base
CK = Competition Knob
SB = Super Base
SK = Super Knob (with long sleeve)
TB = Tulip Base
Another view of a Competition with Super Knob and Super with Competition Knob:
http://pccab.net/Joysticks2.jpg