Bitmain CLAIMED something like a 25% annual return on those, but the real return was closer to 12%, which wasn't bad.
The V4 contracts are CLAIMED to be 12% or something like that, actual number crunching shows more like a 6-7% return IF THE HALFING DOESN'T KILL THEM OUTRIGHT PREMATURELY (and right now, it looks like the halfing WILL kill them given recent diff increase trends).
I strongly suggest IGNORE THE BLOODY V4 CONTRACTS, way too high a risk of LOSING money and very poor return.
Right now, it looks like the BW.COM B-Twelve contracts are the best option of that type.
I did not look into BW.com B-Twelve contracts but like QuintLeo I did own the pacmic v3 and earned about 3% in 3 months or 12% in a year projected.
My contracts all ended in about 84-90days.
I now own more then 6000gh in s-7 as hash. On hashnest