This study will evaluate the clinical efficacy and safety of the BTL-899 device for toning of buttocks. The study is a prospective multi-center open-label two-arm study. The subjects will be enrolled and assigned into two study groups. The subjects will be enrolled and assigned into two study groups; HIFEM+RF (HR) and HIFEM (H) group. Subjects of both groups will be required to complete four (4) treatment visits and two follow-up visits.

Inclusion Criteria:

• Age > 21 years
• Voluntarily signed an informed consent form
• BMI ≤ 35 kg/m2
• Women of child-bearing potential are required to use birth control measures during the whole duration of the study
• Subjects willing and able to abstain from partaking in any treatments other than the study procedure to promote body contouring during study participation
• Subjects willing and able to maintain her regular (pre-procedure) diet and exercise regimen without affecting significant change in either direction during study participation

Exclusion Criteria:

• Electronic implants (such as cardiac pacemakers, defibrillators, and neurostimulators)
• Metal implants
• Drug pumps
• Malignant tumor
• Pulmonary insufficiency
• Injured or otherwise impaired muscles
• Cardiovascular diseases
• Disturbance of temperature or pain perception
• Hemorrhagic conditions
• Septic conditions and empyema
• Acute inflammations
• Systemic or local infection such as osteomyelitis and tuberculosis
• Contagious skin disease
• Elevated body temperature
• Pregnancy, postpartum period, nursing, and menstruation
• Intrauterine device (IUD)
• Swollen or neoplastic tissues, space-occupying lesions or skin eruptions in the treatment area
• Basedow's disease