Specs from the 3900 series:
Dimensions (HxWxD) 5.3 x 3.3 x 0.62 in (133mm x 84mm x 16mm)
Weight 6.7 oz. (190 grams)

And the 3600 specs were:
Dimensions (HxWxD) 5.11 x 3.28 x 0.62 in (12.99 x 8.33 x 1.57 cm
130 x 83.5 tapering to 77.5 x 15.9 mm)
Weight 6.3 oz (178.6 g)