I am almost 100% sure it is a 1 1/8 steerer.
In theory, a 381 is 1" (EC30 headset) and a 381i is 1⅛" (IS headset), but I couldn't find yours in the catalogue so it may be transitional.
I just measured the inner diameter of the remaining headset bearing..its a ouch under 3cm so 1 1/8 it is..
@seb1977 started
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In theory, a 381 is 1" (EC30 headset) and a 381i is 1⅛" (IS headset), but I couldn't find yours in the catalogue so it may be transitional.