A lock ring assembly comprising: an inner tubular and an outer tubular (9, 16), the inner and outer tubulars (23; 9, 16) being telescopingly arranged; and a lock ring comprising: a thread profile having one or more formations formed on an outer circumference of the lock ring for engagement with a suitable thread profile formed on an inner circumference of the outer tubular (9, 16); and one or more teeth formed on an inner circumference of the lock ring, the teeth being adapted to dig into an outer surface of the inner tubular, wherein each formation of the profile comprises a flank face and a cut back rear face, wherein the cut back rear face is configured for engagement with a complementary cut back rear face of the profile formed on the inner circumference of the outer tubular (9, 16) such that when the cut back rear face is in engagement with the complementary cut back rear face of the profile, the teeth are moved away from the inner tubular for ease of movement of the lock ring and the outer tubular (9, 16) relative to the inner tubular during assembly of the lock ring assembly, wherein the one or more teeth are configured to permit the lock ring to be pushed along the outer surface of the inner tubular when pushed by the outer tubular (9, 16) in one direction, and wherein the flank face is configured for engagement with a complementary flank face of the profile formed on the inner circumference of the outer tubular (9, 16) to dig the teeth into the outer surface of the inner tubular when the lock ring is pushed by the outer tubular (9, 16) in the other direction in order to prevent the lock ring from moving in the other direction relative to the inner tubular. an inner tubular and an outer tubular (9, 16), the inner and outer tubulars (23; 9, 16) being telescopingly arranged; and a lock ring comprising: a thread profile having one or more formations formed on an outer circumference of the lock ring for engagement with a suitable thread profile formed on an inner circumference of the outer tubular (9, 16); and one or more teeth formed on an inner circumference of the lock ring, the teeth being adapted to dig into an outer surface of the inner tubular, wherein each formation of the profile comprises a flank face and a cut back rear face, wherein the cut back rear face is configured for engagement with a complementary cut back rear face of the profile formed on the inner circumference of the outer tubular (9, 16) such that when the cut back rear face is in engagement with the complementary cut back rear face of the profile, the teeth are moved away from the inner tubular for ease of movement of the lock ring and the outer tubular (9, 16) relative to the inner tubular during assembly of the lock ring assembly, wherein the one or more teeth are configured to permit the lock ring to be pushed along the outer surface of the inner tubular when pushed by the outer tubular (9, 16) in one direction, and wherein the flank face is configured for engagement with a complementary flank face of the profile formed on the inner circumference of the outer tubular (9, 16) to dig the teeth into the outer surface of the inner tubular when the lock ring is pushed by the outer tubular (9, 16) in the other direction in order to prevent the lock ring from moving in the other direction relative to the inner tubular. a thread profile having one or more formations formed on an outer circumference of the lock ring for engagement with a suitable thread profile formed on an inner circumference of the outer tubular (9, 16); and one or more teeth formed on an inner circumference of the lock ring, the teeth being adapted to dig into an outer surface of the inner tubular, wherein each formation of the profile comprises a flank face and a cut back rear face, wherein the cut back rear face is configured for engagement with a complementary cut back rear face of the profile formed on the inner circumference of the outer tubular (9, 16) such that when the cut back rear face is in engagement with the complementary cut back rear face of the profile, the teeth are moved away from the inner tubular for ease of movement of the lock ring and the outer tubular (9, 16) relative to the inner tubular during assembly of the lock ring assembly, wherein the one or more teeth are configured to permit the lock ring to be pushed along the outer surface of the inner tubular when pushed by the outer tubular (9, 16) in one direction, and wherein the flank face is configured for engagement with a complementary flank face of the profile formed on the inner circumference of the outer tubular (9, 16) to dig the teeth into the outer surface of the inner tubular when the lock ring is pushed by the outer tubular (9, 16) in the other direction in order to prevent the lock ring from moving in the other direction relative to the inner tubular.