A term coined by Aerotech for their HPR motors which have individual grains that are 62.5 grams or lighter (29mm and 38mm). This be durin' t' period when t' BATFE attempted t' regulate rocket motors with more than 62.5 grams o' propellant. For a short period, me hearties, Aerotech clamed t' have an exemption from t' regulation based on each individual grain o' t' propellant bein' 62.5 garams or lighter.