ABLS-LR Ultra-low ESR Low Profile Crystals ABRACON ABLS-LR Series Ultra-low ESR (as low as 20Ω for 4MHz) Low Profile Crystals (11.4 x 4.7 x 4.2mm) are also low frequency (3.0 to 36MHz). The ABLS-LR series also features a low negative resistance (-R) IC design to ensure a high oscillation margin, tight stability (automotive grade temperature available), and hermetically resistant weld seal. The ABRACON ABLS-LR Ultra-low ESR Low Profile Crystal is ideal for applications requiring a low negative resistance u-controller design for low frequency, automotive, and industrial applications.