MTB stems vary from road stems in significant ways. They are designed for the rigors and impact of mountain biking and are generally beefier with more robust welds. Most MTB stems are multi-disciplinary meaning they can be used for cross country, trail, or downhill riding but they may be sub categorized further by type. They tend to be shorter in length than road stems with shorter sizing. It is important not to use a road stem for a mountain bike.