It's a special shape that mates to the inside of your head tube. The bearing it a bit thicker than a standard bearing as it is the load bearing widget rather than the traditional cups. You'll either need to order it in special through your merida dealer of take the frame to a bearing specialist for correct fitment. If you have a part number that would help. If you haven't figured it out yet I'm just making shit up.
I'd like to add some firsthand info on this.
My merida big 7 carbon edition (2014) was listed as having this headset.
The headset is a ZS40/28,6 - ZS55/40 but Merida (FAS) call it big conoid. Conoid just mean "approximately conical shape" and is a rather poor spec.
I used https://blue.canecreek.com/headset-fit-finder to get the headset specs but it missed on the lower headset spec (said ZS56/40 not ZS55/40, thankfully the bearing I had on hand fit into the original lower cup and got on).
In conclusion, use caliper to verify the dimensions you need on the bearings and so on, and be prepared for the eventuality that the components may disintegrate on opening the headset if it is in poor condition.
Dunno, I never bothered to ask the shop, wanted to figure it out on my own.
This thread is incidentally on top on google on the merida conoid headsets which is why I wanted to add info.
Especially as I had same question as OP 3 years after and no real clear answer here (or elsewhere).