They both are, Savox copied them. The only difference is the specs. below:
9551-
Modulation:
Digital
Torque:
4.8V:
98.0 oz-in (7.06 kg-cm)
6.0V:
122.0 oz-in (8.78 kg-cm)
Speed:
4.8V:
0.14 sec/60°
6.0V:
0.11 sec/60°
Weight:
1.59 oz (45.0 g)
Dimensions:
Length:
1.61 in (40.9 mm)
Width:
0.79 in (20.1 mm)
Height:
0.98 in (24.9)
9550-
Basic Information
Modulation:
? (add)
Torque:
4.8V:
66.6 oz-in (4.80 kg-cm)
6.0V:
83.3 oz-in (6.00 kg-cm)
Speed:
4.8V:
0.11 sec/60°
6.0V:
0.09 sec/60°
Weight:
1.55 oz (43.9 g)
Dimensions:
Length:
1.59 in (40.4 mm)
Width:
0.82 in (20.8 mm)
Height:
1.00 in (25.4 mm)