These are high quality bi-polar (non-polarized) electrolytic capacitors that are use most commonly in passive crossovers. They are to be wired inline with your speakers positive terminal to block out the bass.
They feature a 5% dissipation factor and are rated at 100V which are effective to approximately 200 watts.

These come sold in pairs, enough to do one pair of speakers. You will use one per speaker positive terminal. The sound needs to go through this before it gets to the speakers positive terminal for it to filter properly. 
I include some extra heatshrink for you to help insulate them when installing.

Key Features
12 microfarad value
10 mm diameter x 24 mm long
5% dissipation factor 
100 VDC working voltage
±10% tolerance
 
When used on:
 
4 ohm driver the cap will give a 6db/octave high pass slope starting at 3.3Khz
 
8 ohm driver the cap will give a 6db/octave high pass slope starting at 1.65Khz
 
If you have a different driver then please refer to the capacitor calculator.