Type FK Connects round tube parallel to the surface Dimensions (mm) FK 12 FK 18 FK 25 FK 30 FK 40 FK 50 A 12 18 25.1 30.1 40.15 50.2 B 5.3 5.3 6.5 6.5 8.5 10.5 C 18 18 30 30 42 50 D 25 25 40 40 56 66 E 25 25 40 40 60 65 G 35 35 55 55 78 92 H 38 38 53 53 82 98 K 32 32 52 52 71 83 L 38 38 60 60 83 96 M 50 50 78 78 108 128 N 5 5 7 7 10 14 O* n/a n/a n/a n/a 52 62 P 23.5 23.5 33 33 48 58 S M6x25 M6x25 M8x35 M8x35 M10x50 M10x60 Note * FK12 to FK30 have two centrally placed holes, therefore dimension O is not applicable.