This actually popped up some time ago, and I completely ignored it. See, The Prop Store of London just offered a rubber Inara arrow, so when this showed up I thought it was the same one — just ten bucks more — and didn't look closer. Turns out this is, in fact, a wood-and-metal one.

This arrow is made out of a light wood, has black feather fletching and a light metal tipped pointes. The bow and arrows were used by Inara in the end scenes when the group face the Reavers, but during post-production, the weapon was replaced by a gun with the use of CGI. The arrow measure 78cm (30.5”) long.

Always double check yourself, kids. Important safety tip, especially when dealing with arrows.