Sunny Health & Fitness SF-B1004 - Manual (Page 16)

Connect the Backrest Stem Support (6) to the Saddle support (5) with
2 x M8 Flat Washers (14), 2 x M8 x 50 MM Carriage Bolt (15) and
5.
Fix the Backrest (19 ) to the Backrest Stem Support (6) with 2 x M8 x 40 MM (13)
6.
Page 15
Assembly & Adjustments
and 2 x M8 Flat Washer (14).
6
14
15
16
5
14
13
19
6
2 x M8 Nylon Nut (16).