Inclusion Criteria:  At least 18 years of age  • Individual who has either: oAnewlycreatedAVfistulaorgraft(surgicalorendovascular)andiscurrentlywaitingforitto mature, or oAfunctioningAVfistulaorgraftandatelevatedriskforastenoticevent,asdeterminedbyeither clinical judgement or diagnostic testing  Competent and willing to provide written informed consent to participate in the study Agrees to perform the protocol-mandated testing procedures  Exclusion Criteria:  • Pseudoaneurysm on the measured AV access  Transposed AV fistula Skin near the proximity of the AV access that is swollen, infected and/or inflamed, or has skin eruptions, open wounds, or lesions Major cardiovascular surgery (not related to the vascular access), hospitalization, or systemic infection within the last 2 weeks Participants with novel indications for their arteriovenous fistula (AVF) or arteriovenous graft (AVG), such as HeRO grafts. AVF/AVG in a non-arm location (e.g. leg, abdomen or chest-wall) Pregnancy (if female and sexually active, participant must be using a reliable form of birth control, be willing to sign a waiver, be surgically sterile or be at least 2 years post-menopausal) Serious medical condition which, in the opinion of the investigator, may adversely affect the safety of the participant or the device being evaluated