AUDIOPIPE 5.25" 6.5" 99 UF BASS BLOCKERS 400Hz @ 4 OHM 5-1/4" 6-1/2" 4 PCS Bass Blockers BB-99 Removes sounds that are below a certain frequency Designed to enhance the performance and power handling of tweeters and midrange speakers by removing frequencies beyond their capabilities Frequencies Blocked: 4 Ohms: 0-400 Hz and up / 8 Ohms: 0-200 Hz and up Encased in shrink tube with wire leads for easy installation