Grillos's User Friendly

Grillos's User Friendly is an innovative mayfly pattern designed by Anthony Grillo that combines proven materials in a uniquely effective configuration. This versatile dry fly features a foam back for unsinkable floatation, a purple dubbing body that fish find irresistible, and a smoke macrame yarn wing that provides excellent visibility. The white rubber legs add subtle movement while the grizzly hackle ensures proper flotation and a realistic footprint on the water.

Grillos's User Friendly fly pattern - imitates Mayflies, Blue-Winged Olive, Pale Morning Dun tied for Trout
  • Intermediate
  • Spring, Summer, Fall
  • Trout
  • Size 12–16

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Grillos's User Friendly is an innovative mayfly pattern designed by Anthony Grillo that combines proven materials in a uniquely effective configuration. This versatile dry fly features a foam back for unsinkable floatation, a purple dubbing body that fish find irresistible, and a smoke macrame yarn wing that provides excellent visibility. The white rubber legs add subtle movement while the grizzly hackle ensures proper flotation and a realistic footprint on the water.

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Materials

Hook
XC110BL-BN, size #12–#16
Thread
Black Veevus 14/0
Tail
Tan or Dun Mayfly Tails
Body
Purple Antron Dubbing
Back
1MM Black Razor Foam
Wing
Smoke Macrame Yarn
Hackle
Grizzly Rooster Cape or Saddle
Thorax
Purple Ice Dub or Antron Dubbing
Legs
White Fine Round Rubber Legs

Overview

This Charlie Craven pattern from Charlie's Fly Box showcases Anthony Grillo's creative approach to mayfly imitations. The User Friendly combines foam-backed durability with the fish-catching appeal of purple dubbing - a color that has proven effective on selective trout. The foam back ensures the fly floats indefinitely even after multiple fish, while the macrame yarn wing provides the angler with excellent visibility without appearing unnatural to the fish. The grizzly hackle and white rubber legs complete the buggy profile.

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Behavior & presentation

Natural Behavior
Small Baetis mayflies emerge during overcast weather in dense congregations, each dun perching upright on the surface with wings gradually expanding. The olive-bodied adults remain vulnerable for 10-20 seconds per emergence, their dark wing silhouettes contrasting with pale bodies as they prepare for flight from predictable current lanes where emergence concentrates.
Where Trout Eat It
Trout strike this during BWO and PMD hatches in both slick water and turbulent freestone runs.
How to Fish It
Dead drift on 4X-5X tippet. The foam back needs no floatant and supports substantial dropper weight.
Best Water
Fast riffles and slick flats where buoyant foam keeps fly floating through varied currents.
Strike Type
Selective risers sip with metronomic rhythm—watch for repeating rise rings in the same feeding lane as fish establish predictable timing, then set gently with a lifted rod tip when you see the take.

Fishing strategy

Rigging Suggestions
Fish on a 9-foot leader tapering to 4X-5X tippet. The buoyant foam construction makes this an excellent indicator fly in dry-dropper rigs.
Seasonal Timing
through fall mayfly hatches, particularly during BWO and PMD emergences when the purple coloration seems to trigger more strikes than natural-colored patterns.
Pro Tips
Adjust presentation depth and speed based on fish activity level and current conditions for best results.
From River & Run

Where to fish it

Rivers anglers pair with this fly, with local shops that stock it.

Open River & Run

River details and fly shops from River & Run, our sister site.

Entomology

Small mayfly duns emerge in dense numbers during predictable hatch windows, riding the surface film with upright wings while completing final wing expansion. Blue-winged olive species often hatch during overcast or inclement weather when lower light levels increase their vulnerability period. Their consistent size and profile allow fish to establish selective feeding rhythms, methodically rising to intercept duns in preferred current lanes where emergence concentrates.

Order
Ephemeroptera
Family
Baetidae
Common name
Blue-Winged Olive
Organism
insect
Life stage
dun

Pattern details

  • Moving Water
  • Rocky Mountain
  • dead-drift
  • baetis-hatch
  • modern
  • searching-pattern
  • low-clear-water
  • freestone

Get this fly

Grillos's User Friendly, tied and ready to fish

Hook #12 to #16 · Intermediate