27 CFR §5.142

1. (a)The class neutral spirits. “Neutral spirits” or “alcohol” are distilled spirits distilled from any suitable material at or above 95 percent alcohol by volume (190° proof), and, if bottled, bottled at not less than 40 percent alcohol by volume (80° proof). Neutral spirits other than the type “grain spirits” may be designated as “neutral spirits” or “alcohol” on a label. Neutral spirits (other than the type “grain spirits”) may not be aged in wood barrels at any time.
2. (b)Types. The following chart lists the types of neutral spirits and the rules that apply to the type designation.