Unit types

WS 120 Trio without preheating register	WS 120 Trio with preheating register
WS 120 Trio LR	WS 120 Trio LRV
WS 120 Trio LL	WS 120 Trio LLV
WS 120 Trio QR	WS 120 Trio QRV
WS 120 Trio QL	WS 120 Trio QLV

L = Ventilation unit with longitudinal flow
Q = Ventilation unit with transverse flow
R = Right-hand version
L = Left-hand version
V = Preheating register

Example WS 120 Trio LLV = Ventilation unit with longitudinal flow, left version, with preheating register