Deltac does not specify a dimension for how much the slide lock is extended or an overall length, please contact them directly for these dimensions. They will not effect holstering the Gen 5 Glock. The OEM Gen 5 slide lock for the same model glocks can be found here:
https://www.opticsplanet.com/glock-oem-slide-lock-gen-5.html
I just installed this on my G34 G5. This gun is a range gun for me, NOT a carry gun. I have a generic nylon size 04 Allen holster. This does not affect holstering, or drawing, my G34 from my holster. I do not know exactly how much more extended, this extended slide release is ... but, it is enough to make disassembly much easier ... however, when I slide a business card along the side of my G34 frame, it does NOT catch on the extended slide release ... so, I think that this extended slide release does NOT project beyond the slide release finger groove in the frame.