Seiro (wooden steamer with the bottom made of reeds) is also used as a serving dish for soba but, even if soba is served in a seiro, it is still identified as zaru soba as long as there is nori on top.
また、蕎麦の器には「せいろ」もあるが、せいろに乗った蕎麦でも海苔がかかっていればざる蕎麦である。