The cuff is supposed to go on your left arm. This brings the closure flap under your arm next to your body. It takes some gymnastics to hold the spring portion of the cuff down with my chin in order to pull the velcro fastener closed so you don't get a very common E1 error (cuff too loose). It does work easier for me on my right arm---and the fine print says you can use it on your right---because you are then pulling the fastener part up and over. Hard to explain...you have to do it to understand.
It seems accurate but unless I have someone take my b/p with a stethoscope and a cuff it is hard to really tell.
One annoying thing--- I have a pacemaker. It records every single heartbeat I have. I see my doctor regularly and I've not had irregular heartbeats. The Omron tells me at every reading I have an irregular heart rate. I think the built in EKG machine in my chest may be a tad more accurate.
The cuff does fit my wide arm. I like that. However it is so long that in order to place it 1/2-1" above my elbow it is just about in my armpit. If all you want is accurate and you are, perhaps, more dexterous than I am it will serve you well.