Hi, for the thigh opening measurement, it is about 26cm,it can be stretch to 41cm. Because the design is medium to low waist, so please measure at the low to medium part of waist. And please measure the length of hip as well. For free gift, please state in memo to seller and we will send out as per your request. And FYI, althought most of panty are free size, they are from different supplier, so the size are different, the suitable range is different also, please refer to the suitable range details on our item page. Thanks.