Strollers, called "Masonic Suits" in England, are the preferred dress at Assemblage meetings,
as well as meetings of most Masonic orders of English origin (St. Thomas of Acon, Scarlet Cord, Masonic Order of Athelstan, etc.)
Here are a few sources for strollers:

A stroller consists of:
Suit jacket in black or dark (charcoal) gray
Vest in same fabric as jacket, or dove gray wool, buff or fawn linen
Hickory stripe (black and gray) formal trousers, or black and white checks
White dress shirt with laydown collar
Black dress shoes (not patent leather)
Operatives necktie (or the necktie of whatever Masonic order you are
attending)