I am normally filming in the US and have the usual LOWEL RIFA Softboxes with 750W Tungsten Lamps, but I do get over to the UK and was looking for something that offered 'comparable lighting' in a travel size and at a low price.
I am very satisfied with the Westcott 43-inch Optical Satin Umbrellas. I pair them with Lowel 750W Tota lights that are attached to light stands using a Manfrotto Umbrella shoe. I must stress that if you buy these umbrellas you will want the shoe from Manfrotto or something like it because the base of the rod is larger than a standard Lowel 1/4" umbrella hole.
Anyway -- I left the black fabric on the back and bounced the light down at 75 degrees on my subject all day for 4 days and the lighting was excellent and the umbrellas did a super job.
No, I don't think it is comparable to the RIFA Softbox which sells for $900 in the USA, but it doesn't cost that as well and is far more transportable. Unlike large softboxes, these lights can attach to the lightweight light stands for sale here as well and don't require sandbags or weights for stabilization when using a lightweight light head like a Lowel Omni or Tota light.
The light color is a warm honey / tungsten neutral white using 750W, probably a bit warmer using a lower wattage head.
Once the job was done, the umbrellas collapsed to about 12 inches long and 2 inches wide and stored in a typical umbrella nylon sleeve and then inside a plastic sleeve. A lot of product for the money.
HIGHLY RECOMMENDED FOR VIDEO PRODUCTION.