This is the XL Micro Servo Arm set by Dubro. FEATURES: Plastic construction INCLUDES: (4) Single-sided servo horns (2) Dual-sided servo horns REQUIRES: Futaba 3108M S3110M, Hitec HS-50/HS-55, E-Flite S75 servo SPECS: Single-sided horn length: 28.70mm Dual-sided horn length: 51.45mm JBM 1-11-06 ir/jxs