Finding your fit
A well-fitting device should feel secure without pinching, numbness, or coldness. This guide walks through how to measure, how CB-X kit sizes compare, and a simple calculator to suggest a starting point. Tube length is only one part of fit—each complete kit also includes multiple U-rings and spacers so you can tune ring size and gap.
For the manufacturer's full guide and support, see the CB-X sizing guide.
Why sizing matters
- Comfort for daily wear and normal movement
- Stable placement without painful pressure points
- Easier hygiene and urination when the tube length matches your flaccid profile
- Reduced temptation to "cheat" the fit with a cage that is far too large
Measure in three steps
Use a soft measuring tape (or string + ruler). Record inches so you can line up with the chart and calculator below. Repeat on a few different days and times; use the measurement you see most often—not right after a hot shower or when aroused.
1. Length (flaccid)
Press the ruler or tape against the pubic bone at the base of the shaft and measure to the tip of the glans. The penis should be fully flaccid.
2. Shaft girth
Wrap the tape around the midpoint of the shaft. Snug, not tight—you should be able to slide a finger under the tape without digging in.
3. Base / ring area
Starting at the top of the penis, pass the tape behind and under the scrotum and back up to meet the start, where the base ring will sit. Keep the tape close to the skin without overtightening.
Calculator
Sizing calculator
Enter flaccid measurements in inches. The suggestion uses shaft length vs. published tube lengths; U-ring fit depends on base girth—kits include multiple rings to fine-tune.
- Shaft diameter (from circumference)
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- Base diameter (from circumference)
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Suggested starting kit (by length)
Enter shaft length to see a suggestion.
This is an estimate based on averages. Anatomy and comfort preferences vary. If you are between two lengths, beginners often prefer the larger tube; experienced wearers may prefer a snugger fit. When in doubt, contact CB-X customer service or your retailer.
Kit length comparison
Approximate tube length and inner diameter (I.D.) of the cage portion for common CB-X kits. Always confirm specs on the product page before you buy.
| Kit | Cage length (approx.) | Cage I.D. (approx.) |
|---|---|---|
| Mini-Me (XXS) | 1¼" (31.8 mm) | 1⅜" (34.9 mm) |
| Mr. Stubb (XS) | 1¾" (44.5 mm) | 1⅜" (34.9 mm) |
| CB-6000S (S) | 2½" (63.5 mm) | 1⅜" (34.9 mm) |
| CB-3000 (M) | 3" (76.2 mm) | 1 7/16" (36.5 mm) |
| CB-6000 (L) | 3¼" (82.6 mm) | 1⅜" (34.9 mm) |
| The Curve (XL) | 3¾" (95.3 mm) | 1½" (38.1 mm) |
Beyond the numbers
- Anatomy vs. chart: Pick the tube closest to your flaccid length. If you match one size exactly, some first-time wearers size up one step for a bit more room.
- Snug vs. roomy: A shorter tube feels more restrictive; a longer one can feel easier for long sessions if security is still adequate for your goals.
- Weight change: Base-ring fit tends to shift more than tube length if body composition changes—swap U-rings as needed.
- Showers vs. growers: Large flaccid-to-erect difference sometimes means choosing slightly more tube length than the bare minimum so daytime comfort stays reasonable.
12-hour trial
For a new device, try a full waking day (up to ~12 hours) before planning multi-day wear. Remove immediately if you have pain, numbness, discoloration, or anything that feels wrong. Chafing can sometimes be improved with a skin-safe moisturizer and better ring sizing.
Quick FAQ
Between two lengths? Consider experience level (newer wearers often pick the larger tube), how strict you want restriction, and whether you prioritize long-session comfort.
How do I know it fits? Snug and secure, no ongoing pain, normal circulation, and you can urinate without constant mess—fine-tune with spacers and rings from the kit.
This page is for general education. Individual results vary. CB-X is a registered trademark of its owner; Locktober is not affiliated with CB-X beyond offering compatible products where applicable.