Experience with winter frost?

New millenium’s winter frost looks interesting and wondered if anyone has experience with it… How and when used? Noticable difference? And how is it used to control height or stretching as it is advertised to do? £45 a bottle to use for 5-7 days. Should do something. Gonna try this time in 2 to 3 weeks unless I hear otherwise. Will or won’t buy next week