A Clinical Investigation Comparing the Safety and Performance of RefillHA Solid With Hydryalix Ultra Deep Lidocaine for the Correction of Moderate-to-severe Nasolabial Folds

Inclusion Criteria: * Men or women of any race, 18 years of age or older. * The presence of moderate to severe bilateral NLFs each with WSRS score of 3 or 4. * NLFs of the same WSRS grade on the left and right sides of the face. * Willing and able to read, understand and sign the informed consent. * Willing to adhere to the protocol and to comply with the requirements of the entire investigation (ability to attend all the planned investigation visits according to the time limits included and report events and concomitant medication for the entire duration of investigation). * Agree not to undergo other treatments or cosmetic procedures in the treatment area during the study, such as botulinum toxin, hyaluronic acid injections, facial laser treatments, fat injections, any other permanent or semi-permanent facial dermal fillers. * Female subjects of childbearing potential must have a negative urine pregnancy test and must adopt an appropriate method of contraception for the entire duration of investigation. Exclusion Criteria: * Pregnant (as determined by a urine pregnancy test at the screening visit) or lactating women. * Prior treatment (i.e., other permanent or biodegradable injectable fillers or surgical correction such as a face-lift, etc.) within 3 months prior to entry into the study or planned to undergo such treatment during the study. * Previous treatment with permanent implants (e.g., silicone) in the area to be treated. * Subjects who are currently or recently treated with laser, ultrasound or peeling, and who have not fully recovered from these treatments. * Presence of active inflammation, infection, or unhealed wound of the face, such as acne, herpes, dermatitis, scaring etc. * Presence of varices in the area to be treated. * History of hypertrophic scarring. * Metabolic or endocrine serious diseases (e.g., uncontrolled diabetes or diabetes complications), anaphylaxis, severe allergies, immune disorders affecting the skin or other local or systemic concomitant diseases that may interfere with healing. * Current neoplastic (including skin cancer) and/or immunodepressive diseases. * Known hypocoagulability state. * Have received anti-coagulation, anti-platelet, or thrombolytic medications (e.g., warfarin), anti- inflammatory drugs (NSAIDs such as aspirin, ibuprofen), or other substances known to prolong time of coagulation from a week before treatment. A wash-out period of a week is allowed. * Use of narcotic agents, antineoplastics, immunosuppressants or any other agent that may interfere with wound healing in the months before the screening visit. * History of severe allergic/anaphylactic reactions or multiple allergies. * Subject, who has a condition or is in a situation that, in the investigator's opinion, may put the subject at significant risk, or may significantly interfere with the patient's participation in the study or with protocol evaluation parameters. * Subjects considered to be unsuitable to participate, in the investigator's opinion, for any other reason. * Subjects with known allergy or hypersensitivity to at least one component of any of the study medical devices.