ZERO DEGREE INTERDISC
The 0 degree interdisc (blue) creates 6 degrees on the sidefins (existing splay already inbuilt) and 0 degrees on the centre fins. The centre box should only ever contain a blue disc.

TWO DEGREE INTERDISC
The 2 degree interdisc (clear) creates 8 degree splay on the side fins, when inserted with the "plus" sign on the rail (adding 2 degrees). When the disc is inserted the other way round (plus sign on the inside) then this discs creates 4 degree splay (deducting 2 degrees from the existing 6 degrees already inbuilt into the fin)

FOUR DEGREE INTERDISC
The 4 degree interdisc (yellow) creates 10 degree splay on the side fins, when inserted with the "plus" sign on the rail (adding 4 degrees). When the disc is inserted the other way round (plus sign on the inside) then this discs creates 2 degree splay (deducting 4 degrees from the existing 6 degrees already inbuilt into the fin)

SIX DEGREE INTERDISC
The 6 degree interdisc (yellow) creates 12 degree splay on the side fins, when inserted with the "plus" sign on the rail (adding 6 degrees). When the disc is inserted the other way round (plus sign on the inside) then this discs creates 0 degree splay (deducting 6 degrees from the existing 6 degrees already inbuilt into the fin)