Glass nibs are breakage-prone, and replacement is hard to obtain. Historical glass-nib fountain pens were produced mainly between the late 1920s and mid-1940s, e.g. as safety or push-fillers; at Montblanc there were corresponding models like 442 and 444, today rare and expensive and able to cost around 500 euros. No-name glass-nib pens are available much more cheaply on eBay in the single-digit euro range. Modern glass nibs are supplied by Dr. Franz-Josef Jansen on de-atramentis.com from about 8 euros. Glass nibs were earlier used for document-proof inks that would clog usual nibs and feeds. With glass-nib pens the maker Haro is only reachable via the second-hand market.