self-fitting

adjective2

1. •
   Of a hearing aid: programmable by the user to suit their own needs.
2. •
   Of a candle: having a specially shaped or tapered base that will fit various different sizes of holder.

   • After a time Mr. John Dormouse and his daughter began to sell peppermints and candles. But they did not keep "self-fitting sixes"; and it takes five mice to carry one seven inch candle. — 1909