A crop usually consists of a long shaft of fiberglass or cane or 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. The thin end is intended to make contact with the horse. The handle may have a loop of leather to help secure the grip. 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. Thus, a true crop is relatively short. The term "whip" is a more common term that includes both riding crops as well as longer types of horse whips used for both riding and ground work. A whip is a little slower than a crop, mostly due to having slightly greater length and flexibility. Crops are designed to back up the natural aids of a rider.