I don't see why not... what makes you doubtful? My Pro Stop (Lee version) fits my Lee holder fine so I assume the Hitech version will fit the Hitech holder..
The Hitech filter holder says it can use spacers to hold 4mm filters and I didn't know what the basic filter size was - is it 3mm as standard?
Astraeus said:But the 100mm Pro Stop above will fit into that modular holder?