Nimbo 2G Lightweight Posterior Walker, Extra Small, Knight Blue CPAP Power Supply One-way valve and filter provides

One-way valve and filter provides hygienic protection which eliminates transmission of vomitus and contagious diseases

for easy insertion and removal of the concentrator

They suggest the following to determine if size Large headgear is needed:

Certification: cULus Listed

6 foot Slim Style CPAP Tube

Nimbo 2G Lightweight Posterior Walker, Extra Small, Knight Blue CPAP Power Supply One-way valve and filter providesThe Nimbo Posterior Walker provides maximum mobility assistance for both adults and children. Choose from five different height settings to experience the perfect customized fit. The Nimbo also features an improved handgrip design for increased comfort, and folds compactly for easy transport and storage. Available in three new colors.