As we all know, for telescopic kelly bar for bore hole drilling, there are many different models, from 3 sections to 6 sections, the piling diameter has 377 series, 394 series, 419 series..., etc. So, what is the biggest piling diameter for telescopic bore hole drilling kelly bar at present?

The size of the following picture of kelly bar is 630-5*26. The pile diameter is 630mm, total 5 sections, each is 26m. The diameter 630mm is the biggest piling diameter kelly bar up to now.