Its a small section inside the shoe that can expand up to 5 millimeters to prevent numbness. Without any extension system, the toes end up on top of each other and tend to get numb.
Louis Garneau Tri X-Speed XZ Shoes 47 Black
Louis Garneau Pink Tri X-Speed II Cycling Women's Size US 9
Louis Garneau Tri X-Speed III Cycling Shoe - Men's - Bike
Louis Garneau Tri Air Lite Triathlon Cycling Shoe – all3sports
Louis Garneau Womens Tri X-Speed XZ Shoes
Louis Garneau Pink Tri X-Speed II Cycling Women's Size US 9 Euro
Louis Garneau Women's Ruby XZ Shoe - Moosejaw
Footwear — Page 2 — Playtri
The Pearl Izumi Tri Fly Pro Shoe is a premium podium-focused shoe designed for speed, comfort, and efficiency to make the most of race day. The upper is constructed from a combination of airy mesh and synthetic leather to maximize ventilation and support.
Pearl Izumi Tri Fly Pro Shoe White
Cycling Shoes Available at Public Lands