Just spotted this over at Bicycle Retailer:
The recalled stems include models BZA, Director, HiFi and Ranger. Only stems with a “Z” marked inside the bolt head are included in this recall. “Chromag” and the model name are printed on the stems. The stems were sold separately from bicycles. Bolts used in the stems are 6 mm in diameter and 20 mm in length. The stems were sold in various colors including black, red, blue, gold, purple and silver.
More details in the full post: http://www.bicycleretailer.com/recalls/2017/04/26/chromag-recalling-about-100-stems-replace-bolts#.WTrolxPyuV4