These Eberspacher heater ducting connector flanges are 75mm nominal external diameter - they are designed to slide within 75mm id ducting. The ducting fits over the outside and then is clamped with a hose clamp. To pass through a bulkhead you would require qty x 2 therefore.

I trust this answers your question, if we can help any further please do not hesitate to email sales@butlertechnik.com

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