Ruderhorn, rotP2 Graupner 1023.R These proven control surface horns are now available in three different colours - red, blue and yellow - so you can now match the horns to the covering film used on the model. The horn height can be adjusted in 0.5 mm increments (one rotation of the linkage lug) within the range 13 to 28 mm. The horn is attached to the control surface using three M2 x 30 screws.