Aparently the Polish people like high-thrust motors - According to this post they've got A15, B15, C15, D15, and D25 motors.
this site (translated) shows A5-4 and B15-5 motors, for about $2.73 for the B15s and $1.82 each for the A5s - comparable to Questes prices. The picture appears to show the A5 as roughly 13mm by 45mm (same as Estes 13mm T motors), the B15 as 18mm by 36mm or so, the C15 as about 18x50, and the D15 as 18x80 or so.
Because of the high thrust and small size, especially for the D15, I would venture that the C and D motors are made with a sort of composite, perhaps similar to the Czech Deltas.
RIP Chuck Berry
3 days ago