The following swing seats have two swing points and can therefore not be fitted to any of the extensions as they only have single swing points.
Wooden Swing Seat No 1
Sling Swing Seat No 2
Deluxe Rubber Swing Seat No 3
Horizontal Tyre No 7
Toddler Swing Seat No 11
Baby High Back Seat No 12
Rings No 16
Trapeze Bar No 12
Trapeze Bar and Rings No 23
Climbing Rope No 25
Rope Ladder No 26
4 Sided Rope Ladder No 26-4
Black Hammock Seat SHS
The Push Me Pull You PMPY can also be fitted onto the central section of the frames or onto the extensions of the larger swing sets such as the TFX, DFNX and similar.
All of the following swing seats have a single swing point and fit on any of the extensions on either the swing frame or net frame :
Monkey Button No 44
Vertical Tyre No 10
Climbing Rope No 25
Hammock Seat SHS
Twizzler No 45
More information about swing points here.