From OS1st:

The first-ever Plantar Fasciitis sock that strengthens the foot structure and prevents Plantar Fasciitis symptom onset as well as overuse injuries. With precise targeted compression levels and cushioning, the FS4 Plantar Fasciitis sock features Compression Zone Technology^® that is designed for proper foot support. 

Targeted Conditions

• Plantar Fasciitis
• Foot Fatigue
• Arch/Heel Pain

Performance Features

• Medical Grade Support
• Y-Gore heel for anatomical shape
• Patented Compression Zone Technology^®
• Seamless Construction
• Extra cushioning without the bulk
• Anatomical left/right design for perfect fit
• Anti-bacterial fabric