[{item:"journal",qty:25,tags:["blank","red"],dim_cm:[14,21]},{item:"planner",qty:75,tags:["blank","red"],dim_cm:[22.85,30]},{item:"postcard",qty:45,tags:["blue"],dim_cm:[10,15.25]}]

db.collection.aggregate([{$match:{dim_cm:{$gt:25}}},{$project:{_id:1,item:1,qty:1,tags:1,dim_cm:{$filter:{input:"$dim_cm",as:"item",cond:{$gt:["$$item",25]}}}}}])