HO scale and 1/87 scale are related because of simple math
3.5mm to the foot
OO and 1/76 are matched up also, again because of simple math
4mm
check your packages,,,,and make sure you aren't keying in and concentrating on only part of the labeling
A lot of items are marketed as "HO/OO" in that range of models and detail accessories in the "just a tad smaller than 1/72 scale"
and most of the time,,,,,the items will be mixed and matched, and no one will come after anyone,,,,,,,back in the day Roco, Airfix, and Esci AFV's all fought alongside each other,,,,,,and they are technically 3 different scales
Rex (old wargamer,,,,until GHQ came along and made my collection obsolete)