A connector arrangement used for connecting and locking tubular members. The connector consists of two tubular members and a coupling member. The tubular members are threaded together to create a threaded connection. The locking arrangement is provided by a pathway formed on the tubular member whereby a locking member can be inserted in to the pathway to lock the threaded connection. The locking arrangement is also provided by a plurality of castellation members disposed on each tubular member. The connector also has a separate coupling member which has opposite right-hand and left-hand threaded ends to threadedly mate with the threads of the two tubular members.