A modern crop usually consists of a long shaft of fiberglass or cane which is covered in leather, fabric, or similar material.
The rod of a crop thickens at one end to form a handle, and terminates in a thin, flexible tress such as wound cord or a leather tongue, known as a keeper.
The handle may have a loop of leather to help secure the grip or a "mushroom" on the end to prevent it from slipping through the rider's hand.
The length of a crop is designed to allow enough leverage for it to be accelerated rapidly with a controlled flick of the wrist, without causing the rider balancing problems.
Loading refers to the practice of filling the shaft and head with a heavy metal (e.g., steel, lead) to provide some heft.