Ground Guitar states that Kirk Hammett uses Ernie Ball Ultra Slinky Guitar Strings (10-48). Additionally, when I attended his Gibson book event and asked him directly, he confirmed that he uses these strings.

This website claims that since 1989, Beck has used Ernie Ball guitar strings in gauges 9-46, 10-48, and 11-48. Because Beck has been using the 10-48, gauge setup since 2011, and Ernie Ball released their Ultra Slinky 10-48 strings in 2019, it is reasonable to assume he uses Ultra Slinkys these days rather than mixing & matching different sets to get the right gauge combination, as he would have pre-2019.

"Jeff’s Guitar Setup"

"This is how Jeff likes his strats set up. The info in the table below info was taken from Dan Erlewine’s book “How To Make Your Electric Guitar Play Great”, Second edition, 2011."

"Some of Jeff’s Todd Krause master-built guitars were examined by Dan, one of which had the strings removed. This allowed Dan to take precise measurements."

Measurement: | Dimensions:

Neck Scale: 25 1/2 ” (648 mm)

Neck Radius: Compound radius: 9 12″ (241 mm) at nut to 12″ (305 mm) at end of fretboard

Bridge Saddle Radius: Between 12″ (305 mm) and 14′ (356 mm)

Fret Size: .098′ X .050″ (2.47 mm X 1.26 mm)

**Strings:
1989: Ernie Ball 9s (9, 11, 16, 26, 36, 46)

2011: Ernie Ball 10s (10, 13, 17, 26, 38, 48)** sometimes increasing string guage to 11s

Neck Relief: 1989: Straight to .006″ relief

Nut: Wilkinson 1st generation nut (slanted on bass side)

Nut height: set up so that with the strings pressed at the 2nd fret there is just enough clearance over the 1st fret to see daylight (.11″ bass side & .006′ treble side).

Neck Action in 1989: At 12th fret – 1/16″ (1.6 mm) bass side 3/64″ (1.2 mm) treble side

Neck Action in 2000: At 15th fret – 1/16″ (1.6 mm) bass side 1/16″ (1.6 mm) treble side

Pole Piece Height: The pole piece heights for the neck, middle, and bridge pickups were all “touching*” (see below) on the bass side and 3/64″ (1.2 mm).

• With the strings off the guitar, Dan laid his straightedge on the frets and then measured the clearance between the straightedge and the polepieces. I don’t really see how this makes the pole piece measurements useful.

"So, you see, there is no real magic here. Jeff can play on any guitar you give him, and it will sound like him. Even when he plays a guitar without a whammy bar, like a Tele, you can recognize his playing almost immediately!"

"Check your guitar measurements against the info in this table to see if any adjustments might improve your playing. Don’t make adjustments to your guitar if you don’t know what you are doing. It’s better to bring it to a qualified guitar technician."

Albert Hammond Jr confirmed via Instagram that he uses Ernie Ball Ultra Slinky Guitar Strings (10-48) on his Stratocaster. This information was obtained through a direct message exchange.

In the YouTube video "Do .13 Gauge Strings Really Affect Guitar Tone?" by Music is Win, Tyler Larson is seen using Ernie Ball Ultra Slinky Guitar Strings (10-48) at the 5:53 mark. He selects a couple of strings from the pack to adjust his guitar setup, addressing issues with high action and an uneven bridge caused by DR DDT strings.

These are seen in the thumbnail and used on the guitar.

Damien J. Stanley showcases his use of Ernie Ball Ultra Slinky Guitar Strings (10-48) on his Instagram account, highlighting them as his choice for optimal performance.