I almost always shoot on-location, which makes portability is a significant issue. Gear that is portable saves time, effort and money to bring gear to the shoot. Perhaps more importantly, with compact gear I can bring more equipment with me and have more options when I shoot.
When Lastolite released the Trifold Umbrella, I was intrigued. It was advertised as 36 inches, large enough to qualify as a versatile medium-sized umbrella, and yet small enough to be used handheld (particularly with the Lastolite Brolly Grip). It was also described as "ultra compact" when folded, which could mean that it would actually fit it in my backpack, making it unnecessary to bring any other bag. It seemed the perfect complement to the Brolly Grip. I went ahead and ordered it and was pleasantly surprised.