Asahi Pentax 67 Extension Tube Set vii This configuration is also useful

This configuration is also useful for mounting where single-axis levels won't read correctly- for example

The Hasselblad 16mm extension tube lets you get a little bit closer with almost any Hasselblad V-mount lens- maybe not close enough for true macro

Like pretty much all of these sort of converters

but all spacing is good

But for a 400mm lens

Asahi Pentax 67 Extension Tube Set vii This configuration is also usefulThis Asahi Pentax 67 Extension Tube Set includes three tubes (14, 28, and 56mm) with autodiaphragm functionality. Works with almost any Pentax 67 lens to provide substantial close focusing capability. In excellent condition.