The patented indicators show exactly when four levels of elongation are reached. Each level of elongation corresponds to a specific amount of applied force. When a level of force is reached the indicator shape will have completely morphed from a rectangle to a square. Lightweight portable and measured repeatability. 5 progressive levels of resistance. Each level has four indicators that show when 50% 100% 150% and 200% elongation have been reached. Cando AccuForce allows for 20 measurable levels of progressive exercise therapy instead of 5 levels. Cando is licensed to use the Thera-Band color sequence so resistance level is easily identified.