You will be hard pressed to find a cap to match the heat of the '18. If it is one with a solid separation between the first and second click, it is one to cherish
@Zoltani .
I only do wooden stems and a particular shrub at that. LOVE 'EM! You are right, wooden stems don't get cleaned. They may need a push-through by a skewer when combusted, but for the most part, the vape oils are a type of wood treatment.
If wooden stems are not lined, you also have to watch for rolling o-rings. Fastest way to destroy a wooden stem.
Most offerings out there will line the insides with a stainless steel or titanium core to make sure the wood, or the resins of 'stabilized' woods, are not part of the airpath. I much prefer my one piece simple stems.