Telescoping are nice but not ideal to adjust while driving. Generally an antenna tuned for the band of interest will perform the best. The tri-band is tuned for 3 ranges. 136-174 420-470 800-900 MHz.
I did not see any of this info listed on Remtronix page, yet zip scanners amazon says,
"25-100%+ POLICE SCANNER RECEPTION BOOST: 6+dB gain over stock handheld police scanner antennas from Whistler & Uniden"
And, you trust Zip Scanners??????
Absolutely the last place I'd personally buy from.
BTW, the previous cut/paste images I posted were from the Remtronix webpage.