For best performance and long term reliability, crossover caps MUST be NON polar FILM capacitors PERIOD.
You should NEVER use electrolytic capacitors for that purpose (well, they may be kludged back to back but forget it). Furthermore, you should pick ones with the highest voltage rating that you can find, since they are subject to AC voltages in the crossover. You can NEVER go wrong with higher voltage ratings. Buy the HIGHEST voltage rated version that you can find. They will be more expensive, but you will sleep better.
If you have accidentally used electrolytics, they will blow almost immediately.
Here are some excellent examples:
https://www.partsconnexion.com/Jantzen-film-caps.html
The silver ones are rated up to 1200 VDC, which is probably ok for about up to 300VAC, which is more than any power amplifier can ever put out and they will outlast your house.