First, welcome to OCC..........
1X8/9 means all the models (Gear & Hydro) that fall into that series.
Gear Drive: [Gear drives end in 8 - even numbers]
*86 - 108 - 128 [ 8 - 10 - 12 HP]
Hydro Drive:[Hydro drives end in 9 - odd numbers]
*109 - 129 - 149 - 169 [10 - 12 - 14 - 16 HP]