EFL4421 replaces PKZ4421 and is used for a variety of models from HobbyZone (e.g. Mini Apprentice S 1.2m, Carbon Cub S 1.3m, etc.), ParkZone (e.g. T-28 Trojan 1.1m, Conscendo 1.5m, etc.), and E-flite (e.g. Apprentice STS 1.5m, Habu STS, T-28 1.1m, Conscendo Evolution 1.5m, etc.).