A step-through frame (aka low-step frame) is a type of with a very low crossbar, typically just above the pedals, or no crossbar at all.

It is most commonly found on utility bicycles. It makes the bicycle more versatile and safer, but also heavier.

Advantages

• there is no risk of stretching or ripping your clothes when mounting the saddle.
• you can wear a skirt (also requires a and possibly a ).
• very quick to mount and dismount, so is suitable for delivery bicycles, or any journey with a lot of stops.
• suitable for old people, or anyone with restricted agility.
• safer than a high crossbar, for several reasons
  • both feet can be placed firmly on the ground when standing astride the bicycle, for instance when waiting at traffic lights.
  • if the rider loses balance, he can step through the bicycle without becoming tangled in it;
  • if the rider is sideswiped or blown sideways, both legs will sweep through the frame and the rider is likely to land safely.

Disadvantages

• heavier, and therefore slower. The frame is substantially thickened and strengthened to compensate for the loss of the primary triangle in the frame geometry.
• fewer places for accessories, eg. a pump or water bottle.