Which SIM card for IPhone 5s, iPhone 6, iPhone 5c & iphone 4s?

Alok, it has nothing to do with what kind of cellphone you use. It depends on what mode your cellphone supports. Normally, there are three modes, GSM, CDMA and WCDMA. If your phone supports GSM and WCDMA, you should buy China Unicom's sim card. If it supports CDMA, you should buy China Telecom's sim card. If it only supports GSM, you need to buy China Mobile's sim card.