10 × 10 PEX Cold Expansion Fittings. Installed using expansion method (expander tool + expansion rings).

https://www.ppsu-pex-fittings.com/product/metric-size-fitting/
Feature
• Material: PPSU
• Connection: Cold Expansion
• Size:10mm-40mm
• 100% LEAD FREE. Corrosion resistant,lighter weight,higher durability than pipes.
• Direct replacement for Uponor Q&E series
• Fully compatible with all types and brands of PEX-a pipe
• WATERMARK, AENOR approved.
• For plumbing, heating & HVAC applications.