US alone. A variety of devices such as nets, harrows, sand rakes etc. have been developed that aid the groundskeeping staff in efficiently collecting these balls from the course as they accumulate. Once collected, they may be discarded, kept by the groundskeeping staff for their own use, repurposed on the club's driving range, or sold in bulk to a recycling firm. These firms clean and resurface the balls to remove abrasions and stains, grade them according to their resulting quality, and sell the various grades of playable balls back to golfers through retailers at a discount. Used or recycled balls with obvious surface deformation, abrasion or other degradation are known informally as "shags", and while they remain useful for various forms of practice drills such as chipping, putting and driving, and can be used for casual play, players usually opt for used balls of higher quality, or for new balls, when playing in serious competition. Other grades are typically assigned letters or proprietary terms, and are typically differentiated by the cost and quality of the ball when new and the ability of the firm to restore the ball to "like-new" condition. The "top grade" balls are typically balls that are considered the current state of the art and, after cleaning and surfacing, are indistinguishable externally from a new ball sold by the manufacturer. Markouts/X-Outs In addition to recycled balls, casual golfers wishing to procure quality balls at a discount price can often purchase "X-outs". These are "factory seconds"; balls which have failed the manufacturer's quality control testing standards and which the manufacturer therefore does not wish to sell under its brand name. To avoid a loss of money on materials and labor, however, the balls which still generally conform to the Rules are marked to obscure the brand name (usually with a series of "X"s, hence the most common term "X-out"), packaged in generic boxes and sold at a deep discount. Typically, the flaw that caused the ball to fail QC does not have a significant effect on its flight characteristics (balls with serious flaws are usually discarded outright at the manufacturing plant), and so these "X-outs" will often perform identically to their counterparts that have passed the company's QC. They are thus a good choice for casual play. However, because the balls have been effectively "disowned" for practical and legal purposes by their manufacturer, they are not considered to