The SLIPIT™, is a group of American-designed folding knives developed by Spyderco. Originating from the UK Penknife (UKPK) project
— the first folding knife to combine their one-hand-opening Trademark Round Hole™, clip carry, and a non-locking mechanism — and drawing inspiration from the Caly series, the group comprises the UKPK, Metropolitan, Urban, and Squeak models. All were designed by Sal Glesser.

The Blue Brother of my Slipit family is the UK Penknife (UKPK) Blue G10 CPM SPY 27 version AKA “The great slicer” or “The Golden Child” as it is made in Colorado when the others are made in Italy.
My UKPK is the G10-handled version in CPM SPY27 steel. It features the thinnest blade (2.5 mm vs 3mm for the other members of the SlipIt family) and offers the best slicing performance, with a cutting edge measuring 75 mm.
You can notice its this G10 version got 4 screws on the handle. (When Spyderco site is only showing 3 screws for their UKPK G10 SPY27 model)
Edit: I got an answer from Golden about that:
“The photo of the G10 model you see online is a photoshopped version of the lightweight model, which only has 3 screws. The 4 screw version is standard for the g10 variant.”
The FRN UKPK got 3 screws and a short spring/backspacer. Perhaps easier to rinse and clean. Its Salt version even exist in yellow with CPM Magnacut and in green with LC200N and also with serrated edge.

On mine, its thin CPM SPY27 blade is particularly well-suited to maintenance by leather stropping, and this model is unique in the group for employing a fork spring, likely necessitated by the longer stainless steel backspacer. Thanks to its blade steel, the UKPK also provides the greatest lateral strength of the series.

Its versatility makes it suitable as a travel knife, steak knife, whittling tool, office companion, or even a light kitchen knife.
You can even change for another style of clip if you want a toolish look.
The UKPK won’t let you down FRN or G10 version. They are great travel non threatening folders.

TECHNICAL SPECIFICATIONS
Overall Length: 6.89in 175mm
Closed Length: 3.95in 100mm
Blade Thickness: .098in 2.5mm
Blade Length: 2.95in 75mm
Edge Length: 2.57in 65mm
Handle Material: G-10
Origin: United States
Steel: CPM® SPY27®
Knife Weight: 2.2oz 63g

The Black Brother of the Slipit family is the Metropolitan, a tad shorter than the UKPK but often described in my book as having “an everlasting edge.” This model is notable as the only Slipit presented here with an FRN (fiberglass-reinforced nylon) handle. FRN is great and solid and the Metro got a full spring/back spacer.

Its key strength lies in the choice of blade steel: Böhler M398, known for delivering extremely long-lasting edge retention at a comparatively very accessible price point. Despite its 3 mm blade stock, the Metropolitan remains an excellent slicer. While M398 offers less lateral strength than CPM SPY27, it excels in edge holding, making this model particularly well-suited as a folding skinner or for heavy-duty tasks such as breaking down cardboard.

TECHNICAL SPECIFICATIONS
Overall Length: 6.31in 160mm
Closed Length: 3.73in 94mm
Blade Thickness: .118in 3mm
Blade Length: 2.68in 68mm
Edge Length: 2.43in 62mm
Handle Material: FRN
Origin: Italy
Steel: M398
Knife Weight: 1.6oz 45g

The Red Brother of the Slipit family is the Urban, my Low Profile London Traveller, produced as an exclusive edition for Heinnie Haynes. This model was acquired at approximately twice the cost of the Metropolitan, owing to its premium blade steel: CPM S90V, a high-performance alloy offering edge retention on par with Böhler M398. Now the FRN Urban is released with M398 too which makes my previous expensive Heinnie S90V Urban quest totally obsolete.

Released prior to the availability of the Metropolitan and the M398 Urban, this knife also features a G10 handle with a distinctive finish. Its compact dimensions allow it to be carried discreetly, such as in the watch pocket of denim trousers. In this collection, the Red Brother is primarily employed as a travel knife for use in London. I have it equipped with the short MicroJimbo clip for the lowest profile possible.

TECHNICAL SPECIFICATIONS
Overall Length: 5.95in 151mm
Closed Length: 3.54in 90mm
Blade Thickness: .114in 2.9mm
Blade Length: 2.49in 63mm
Edge Length: 2.15in 55mm
Handle Material: Red G10
Origin: Italy
Steel: CPM S90V (on mine) M398 for the FRN version.
Knife Weight: 60 gr (for mine) 56 gr for the FRN version in M398.

Big Pizza ? No problemo.

The Silver Brother – The Tweetanium !
The Squeak is truly a jewel within the SlipIt family. Despite its compact size, it never leaves me feeling “under-knived” when carried in a watch pocket.
I once owned a Squeak Deluxe Sprint Run with a titanium handle and Elmax steel blade, which I eventually passed on to JD. Thanks to Guillaume, I was able to acquire another example, new in box.

JD first acquired the original Squeak SC154PBK and used it extensively, praising its thin cutting edge, dependable Böhler N690Co steel, ergonomic handle, wire clip, and reliable one-handed usability.

Later came the titanium sprint-run version, which felt even sharper at the edge, requiring less effort when cutting. Its rounded titanium scales were warm to the touch, slipped smoothly into the pocket, and offered a more refined feel than the FRN model. The stiffer titanium construction also produced a stronger spring, giving the knife a crisper “walk and talk.” While one-hand opening was slightly more demanding, both versions remained capable of the classic “Spydie drop.”
The titanium scales are smooth under the thumb and provide superb ergonomics in a three-finger grip. Construction is minimalist, relying on only two body screws plus one for the deep-carry clip.

This is a three fingers grip when the Urban is still a four finger grip.

This rare titanium variant stands out as a refined upgrade over the standard Squeak—an elegant evolution of an already excellent design.
I love Elmax steel since my Lionspy. I remember beating the crap out of it and it was really forgiving: no chipping and great sharpness. It is tough for a stainless steel.

Its short blade is full-flat-ground, exceptionally thin at the edge, and employs a slipjoint-style “notched-joint” mechanism: the spring holds the blade open during use and offers resistance when closing.

It slice through a Coke bottle butt with its factory edge ! Not many models from the Spyderco line can do that right out of the box.
In practice, performance is outstanding. The small blade slices cleanly through materials such as plastic, wood, ropes and even after extended use—up to a year on my first Elmax Squeak—it remains razor-sharp with only minimal stropping required. Elmax, a rare style among Spyderco knives, is that good !

The Spyder hole and blade spine are the also the sharpest of the family. It could be used to strike some ferro rod.

Compact yet versatile, the “mini micro” knife proves remarkably capable for everyday tasks: cutting meat at the table (where the blade’s belly is especially effective), opening tags, breaking down plastic, and more. It also maintains a discreet, non-threatening presence in public and restaurant settings. It makes a great money clip too.

TECHNICAL SPECIFICATIONS
Overall Length: 5.05in 128mm
Closed Length: 3.05in 77mm
Blade Thickness: .118in 3mm
Blade Length: 2in 51mm
Edge Length: 1.75in 44mm
Handle Material: Titanium
Origin: ItalySteel: Elmax (for mine) N690Co (for the FRN version).
Knife Weight: 69 grams (48 grams for the FRN version)
The Squeak in this titanium version is the heaviest of the family.

Le Choix des Armes

• Blue UKPK – the versatile slicer.
• Black Metropolitan – the non locking hunter’s companion.
• Red Urban – the low-profile city dweller.
• Silver Squeak – three fingers power house.

Each model is reliable, discreet, and delivers outstanding cutting performance thanks to their blade geometry. They shine on the plate and impress with pure slicing ability on the hardest materials (my pastic bottle tests…). Thanks to their relatively strong non locking mechanisms, they also handle whittling tasks—yes, even the Squeak is surprisingly pleasant and powerful against any piece of wood.
And don’t forget, now their slip-joint strength is impeccable. Also each knife comes with a choil, keeping your fingers safe from unwanted blade closure.
Really, when it comes to staying open, Sal Glesser’s four slip-joint designs outclass his excellent Roadie XL—and put Anderson’s COBOL to shame.
Sharp, firm, secure, and reassuring—no surprises when handling these slipjoint knives which are proof that size doesn’t define performance. 😉

Mama Caly can be proud of her slipIt offsprings !