Pulsar is an established thermal brand, and the Helion XP50 family has run through three versions: the XP50, XP50 2 and XP50 Pro. If you own one, the front focus is the control you'll touch most, and this extension makes it quicker to turn, especially with gloves on.
It depends on how far you glass and how much detail you need, so we'd rather talk it through than name one. If you've settled on a Helion XP50, XP50 2 or XP50 Pro, this focus ring fits all three. Call us at (309) 781-8421 if you want help comparing monoculars.