I bought quite a few small items from HK over the past few weeks; some arrived within 2 weeks some are taking longer. Sometimes sellers are located in HK but actually ship from mainland China and from there it takes often much longer. I certainly would not be concerned about 4 weeks. In any case I find HK and Chinese sellers very eager to resolve problems. It may be a good idea to let the seller know that your item has not arrived and tell them you will wait bit longer before lodging dispute. But do not wait past the 43rd day, does not matter what the seller says. 🙂