ive tried solarforce(white) and spiderfire(yellow) rcr123 in my quark 123-2 before, and fit without any problems.
in terms of diameter, its no problem. but i cant say for sure about length, since i never had a quark 123 model.
i also cant recommend getting the ultrafires.... I bought 4x spiderfires, and 4x solarforce RCR123. and within a couple month half of them stop working...
get a couple of AW RCR123 for the same price, and you have better reliability, capacity, and quality.